Category Archives: World Tour Finals

Novak Djokovic and Neutralizing the Second Serve

When Novak Djokovic stands on the other side of the court, you’d better make some first serves.

Djokovic is one of only two players this year to win more than 55% of second-serve-return points (David Ferrer is the other).  When you consider that he also wins more than 35% of first-serve-return points, it’s less clear that the server has much of an advantage.  In fact, when Novak is performing at that level, if his opponent goes through a bad patch and only makes a quarter of his first serves, Djokovic has a better than 50% chance of breaking serve.

Commentators often refer to Djokovic’s return as a weapon, and they’re not joking.  Only six players (including Novak himself and, invariably, John Isner) won as many second-serve points as Novak won second-serve-return points.

What’s most remarkable about his return game is how quickly he neutralizes the second serve, often using tactics that, in the hands of lesser mortals, would be more appropriate for service points.  Unlike other returners, he is somewhat more likely to win a short return point than a long one.  While other players need a few shots to negate the advantage conferred by serving, Djokovic is most effective early in service points.

This graph shows the percentage of second-serve-return points won by Djokovic, by rally length, in four matches I’ve charted (US Open vs Stanislas Wawrinka and Rafael Nadal; Tour Finals vs Wawrinka and Juan Martin del Potro), compared to the the same percentage for other top-ten players (excluding Rafael Nadal) in 19 other matches I’ve charted from the US Open and Tour Finals this year:


When the return lands in play, Djokovic wins almost 53% of return points, while the pack manages less than 44%.  (All of these matches are between top-ten opponents, so the averages are much lower than season numbers, which are affected by matches against lesser opponents.)  The difference stays about the same when we take out 2- and 3-shot rallies.

When we limit our view to points that reach six shots, Novak still has a substantial edge, roughly 48% to 42%.  But in points longer than seven shots, there’s virtually no difference.

Djokovic’s return is so good that if his opponent misses his first serve, the point has turned into a Novak service point.  Opponents are forced to fight their way into their own service points!

This was particularly true in the Djokovic-Nadal US Open final.  (Follow the link, then click the ‘Serve Influence’ tab for a shot-by-shot winning percentage breakdown.)  Nadal won barely half of his second-serve points when Djokovic got his return in play, but once the rally reached five shots (or six, or seven, and so on), Nadal had the edge, winning 60% of points.  From the five-shot mark, Rafa’s advantage only increased.

Of course, Nadal won that match.  It’s not quite so useful to convert return points into service against an opponent whose own return of serve is so effective.  To win today, Novak needs to do more than just attack Rafa’s second serve.  He must either do so even more effectively than he did in New York, or put himself in a better position to win longer return points after the effect of his return has worn off.


Filed under Match charting, Serve statistics, World Tour Finals

Round Robin Shutouts

At this year’s World Tour Finals, we were spared the knottiest sort of round robin tiebreakers.  Each group had a clear winner (Rafael Nadal and Novak Djokovic) who went undefeated, along with another player (David Ferrer and Richard Gasquet) who failed to win a single match.

Since 1987, 33 players have recorded a 3-0 record in Tour Finals round-robin play.  This year is the first time since 2010 (Nadal and Roger Federer) that two players have done so, and before that, we have to go back to 2005 (Federer and Nikolay Davydenko).  It’s not that rare of an event–this year is the 11th time since 1987 that two players have beaten every opponent in their group.

Undefeated players are hardly guaranteed further advances, however.  Those 33 undefeated competitors have a mere 17-16 record in the semifinals, and the 17 men who reached the final won the title only nine times, against nine final-round losses.  (Twice, two undefeated players faced off in the finals–the aforementioned 2010 event along with 1993, when Michael Stich and Pete Sampras contested the title.)

The tiny sample of three round-robin matches pales in predictive value next to the old standby of ATP ranking.  In the last 26 years, the higher-ranked player has won 16 finals.  In the more top-heavy 21st century, the title has gone to the man with the superior ranking 11 of 13 times.  (Advantage: Nadal.)

That said, the gap between the two finalists is traditionally greater than it is expected to be tomorrow.  (If Stanislas Wawrinka upsets Novak Djokovic in the second semifinal, you can disregard this paragraph.  Sorry, Stan, but I’m betting against you.)  Only twice in the round-robin era have the top two players in the ATP rankings met in the concluding match of the Tour Finals–2010 (again) and 2012 (Djokovic d. Federer).

Not a shutout, but shut out

Exactly as many players–33 through 2012–have gone 0-3 in the round robin as the number who did the opposite.  Ferrer and Gasquet find themselves in quality company.

Ferrer is the 7th player ranked in the top three to lose three round robin matches.  In 2001, #1 Gustavo Kuerten was winless, only a year after claiming the championship.  Jim Courier (1993), Juan Carlos Ferrero (2003), and Nadal (2009) went 0-3 from a #2 ranking, while Thomas Muster (1995) and Djokovic (2007) did so while ranked #3.

Ferrer is notable for another dubious achievement: going 0-3 twice.  He previously did so in 2010, so this year, he matches the mark of Michael Chang, the only other man in the round-robin era to post multiple 0-3s, having gone winless in both 1989 and 1992.

His age may work against him, but there is a glimmer of hope for Ferrer.  Four players (including Kuerten, mentioned above) have gone 0-3 at one Tour Finals and won the title at another.  Andre Agassi was winless in 1989, then won the event in 1990.  Stich was 0-3 in 1991, then claimed the title in 1993.  As we’ve seen, Djokovic failed to win a single match in 2007, yet came back to win the tournament in 2008.  (Then did so again last year.)

If Nadal wins tomorrow, we can add one more name to this list, in his case finally adding the trophy to his collection four years after suffering through a winless week.  His 4-0 record so far this week may be no guarantee of success in the final, but it will hardly count against him.

Match reports: I charted today’s Federer-Nadal semifinal, as well as yesterday’s Federer-del Potro match.  Click the links for exhaustive serve, return, and shot statistics.

Worth a read: Carl Bialik analyzes ATP rematches–pairings like Fed-Delpo that faced off in back-to-back weeks.  As usual, we have to rewrite the rules for Rafa.

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Filed under Forecasting, Records, World Tour Finals

David Ferrer and Defiance of the Aging Curve (+Updated WTForecast)

At the end of 2009, aged 27, David Ferrer finished the year with an ATP ranking of 17.  It had been a rough 15 months.  A poor pair of Masters events at the end of 2008 knocked him out of the top five, all the way down to 12.  An indifferent season saw him fall out of the top 20 for a few weeks.  Many players never improve upon their mid-20’s form, so had things gone according to script, Ferrer might still be kicking around the high teens.  His near contemporaries Mikhail Youzhny and Tommy Robredo have followed paths of that nature.

Instead, the Spaniard has only gotten better.  He finished 2010 back in the top ten, at #7.  At the end of 2011 and 2012, he sat at #5.  He’s likely to conclude 2013 at his career-high position of #3.  All this at the age of 31, when many players have shifted focus to their golf games.

This is unprecedented.  Ferrer is only the 12th player of the last 30 years to string together four consecutive year-to-year ranking improvements starting at age 24 or later.  He’s only the second to do so starting at 27, and no one has done it from a more advanced age.  The only other man to match Ferru’s current streak doesn’t really compare: Wayne Arthurs improved his ranking from 1998 to 2002 up to an ’02 year-end position of #52.

Admittedly, this streak is a bit of a sideshow curiosity.  But the underlying issue it reveals is more significant.  Even in an era of 30-something stars on the ATP, tennis is a young man’s game.  At the age when Ferrer began his resurgence, most players are fading, if they’re not already gone.

The exact trajectory of the aging curve depends on the data you choose to examine.  I ran the numbers twice: first with all players in the top 300 since 1983, then limited to players born in 1975 or later.  With the bigger dataset, the apparent peak is at age 23-24.  The average player maintains their level from their age 23 season to their age 24 season, but every year beyond 24 brings with it an increasing decline.  For instance, if we set aside those who disappear from the top 300 entirely, 45% of players improve their ranking in their age 25 season, while 2% maintain it and 53% decline.  At age 26, it’s 38%, 2%, and 60%, while at age 31, it’s 30%, 1%, and 69%.

The following graph shows the percentage of players who improve and decline in the rankings at each age.  While there are still a few guys like Ferrer who post a year-to-year improvement at any age, they are harder to find at each successive age.  Also, keep in mind that the later-career numbers include players returning from injury–Lleyton Hewitt, for example, has improved his ranking each of the last two years.


Limiting our view to those players born in 1975 or later, we have a smaller dataset, but one that should better reflect the current state of affairs.  Here, the peak is one year later, at age 24-25.  Despite the Ferrers, Roger Federers, and Radek Stepaneks who seem to be rewriting the rules, it is still the case that only 42% of 26-year-olds improve their rankings from their age 25 season, while 3% maintain and 55% decline.

Another way of looking at the decline is by measuring and then aggregating the magnitude of ranking changes.  In the dataset limited to 1975-and-later births, he average player loses roughly 2.5% of his ranking from his age 25 season to his age 26 season, and almost 19% of his ranking from age 31 to age 32.  Using this metric, here is a graph of two “decline curves”–ranking position lost at each age.  Both the overall dataset and the more limited, recent dataset are shown:


While the overall direction hasn’t changed from the 80s to the present, the trend in magnitude is clear. At every age in the decline phase, the curve has flattened out, making it a bit more likely that someone like Ferrer would improve throughout his late 20s.

Keep in mind that we’re only measuring those players who remain in the top 300.  Those who retire or fall out of the rankings due to injury aren’t considered, so the actual effect of age–in either dataset–is more severe than these numbers represent.  However, without forcing those guys to play, we can only estimate their aging patterns based on those who do stick around.

Having determined the percentages of players in the current era who improve and maintain their rankings at each age, we can calculate the likelihood that someone would do what Ferrer has done, keeping his ranking moving in the right direction from his age 27 to his age 31 season.  For any individual year, the chances are about 40%, giving us an overall probability of roughly 2.5%, or 1 in 40.  Even limiting our scope to the pool of players in the ATP top 300 at age 27, that seems reasonable–Ferru is, at the very least, a 1-in-40 aberration.

Ferrer’s biggest test yet will be his age-32 season in 2014.  Of players in the current era, 18% of 31-year-olds fall out of the top 300 by the end of their age-32 season.  (In the bigger dataset going back to 1983, 27% disappear.)  Of those who remain, only a quarter improve, and the average ranking change is strongly negative.

Eventually, nature will stop David Ferrer.  Precedents or no precedents, though, he’s a hard man to bet against.  He hasn’t been particularly constrained by nature thus far.

London forecast: After today’s Group B matches, Djokovic is guaranteed a spot in the semis, while Federer’s match on Saturday with del Potro will determine the other semifinalist.  My ratings consider those to be nearly equal on this surface, giving the slight edge to Delpo.  Here is the complete forecast:

Player     3-0  2-1  1-2  0-3        SF      F      W  
Nadal      70%  30%   0%   0%     98.5%  57.9%  33.3%  
Djokovic   73%  27%   0%   0%    100.0%  65.8%  36.3%  
Ferrer      0%   0%  54%  46%     14.7%   5.1%   1.9%  
Del Potro   0%  52%  48%   0%     52.3%  23.3%  10.7%  
Federer     0%  48%  52%   0%     47.7%  20.1%   8.8%  
Berdych     0%  30%  70%   0%     35.8%  11.9%   3.9%  
Wawrinka    0%  46%  54%   0%     51.1%  16.0%   5.2%  
Gasquet     0%   0%  27%  73%      0.0%   0.0%   0.0%

My algorithm doesn’t capture all the complexity of the tiebreak rules, so it’s got Group A a bit wrong right now.  Nadal has locked up a spot in the semis. To clear up any remaining confusion, we’re lucky to have Anna, who lays out the qualification scenarios very clearly for both Group A and Group B.

Today’s matches: I charted both Group B matches today, so there are detailed serve, return, and shot-by-shot stats for each one.  Here is Federer-Gasquet, and here’s Djokovic-del Potro.

Finally, it’s already time to look ahead to Melbourne, as Foot Soldiers of Tennis is monitoring the players on the cusp of direct entry.

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Filed under Aging trends, World Tour Finals

Juan Martin del Potro and Return of Serve Gaps (+Updated WTForecast)

While Juan Martin del Potro isn’t known for his return of serve, it isn’t a major hole in his game.  This year, he has won 38.5% of return points, worse than most of the top 10, but better than Stanislas Wawrinka, Jo Wilfried Tsonga, and about 30 other members of the ATP top 50.

Where del Potro underwhelms is more specific.  Despite effectively returning second serves, he’s far worse than average against first serves.  In 2013, his 28.4% of first-serve-return points won ranked him 36th among the top 50, only 0.1% above Milos Raonic and far behind every other member of the top 10.  Yet Delpo is in the top ten when it comes to second-serve-return points.

Even for a big server like del Potro, it’s difficult to reach the top five without an effective return game.  While he breaks serve less often than any other World Tour Finals qualifier this year, he’s within a percentage point of Wawrinka, Tomas Berdych, and Roger Federer, so it’s clear that statistically, the Argentine is far from being a John Isner-style one-trick pony.

What sets him apart, then, is the enormous gap between first- and second-serve-return effectiveness.  To illustrate the difference, I calculated the ratio of second-serve-return points to first-serve-return points for all eight men in London this week, plus Andy Murray.  Delpo is third among all players with 40 or more tour-level matches this year, while the bottom five names on this list are all in the opposite third of ATP regulars.

Player                  v1W%   v2W%  v2/v1  
Juan Martin Del Potro  28.4%  53.4%   1.88  
Tomas Berdych          30.6%  54.6%   1.79  
Richard Gasquet        30.5%  54.2%   1.78  
Stanislas Wawrinka     30.7%  50.3%   1.64  
David Ferrer           34.5%  56.4%   1.63  
Andy Murray            33.7%  54.7%   1.62  
Roger Federer          32.9%  51.6%   1.57  
Novak Djokovic         35.5%  55.4%   1.56  
Rafael Nadal           35.0%  54.6%   1.56

An aspect–or perhaps a cause–of del Potro’s first-serve-return woes is his knack for letting aces sail by him.  In 2013, 10.5% of his opponents’ first serves were aces, more than any other member of the top 50.  Controlling for opponent serve quality (he did play Isner twice this year), he “improves” to third-worst, ahead of Dmitry Tursunov and Feliciano Lopez.  After this adjustment, we discover that Delpo allowed 22% more aces than an average player would have against the same set of opponents.

When aces are removed from the calculation, del Potro still stands out in comparison to other top players, but he is no longer quite so extreme.  His ratio of second-serve-return points won to first-serve-return points won ignoring aces is 1.55, just a bit higher than Berdych’s 1.53, Richard Gasquet‘s 1.52, and David Ferrer‘s 1.51.

If Delpo gets a racquet on the ball, then, he’s not that much less effective against first offerings than his London competitors.  But he doesn’t get his racquet on as many balls, and however we might manipulate the numbers for fun and profit, the Argentine doesn’t have the option to ignore aces.

So, how much does a poor first-serve return matter?  As with Murray’s infamous second serve, it’s tough to say.  In both cases, the weakness doesn’t keep its possessor from winning big matches against the game’s best, but it might be what is preventing him from ascending from the very top of the rankings.

Were del Potro to improve his first-serve return to the level of the next-worst London participant, Gasquet, it would mean a jump this year from 28.3% of first-serve-return points won to 30.5%.  That would bump up his overall return points won to just short of 40%, and improve his break percentage from its current middle-of-the-pack 23.8% to a nearly-top-ten 26.0%, in the neighborhood of Berdych and Federer.

An improvement of that nature would make Delpo a much bigger factor at the very top of the men’s game.  But like Murray’s second serve, it isn’t that easy.  There’s more than one route to the top–del Potro’s game isn’t so unbalanced to keep him from beating the best players in the world, so perhaps he could more easily improve, say, his second serve than his first-serve return.  It’s tough to tell from the sideline or, especially, the statsheet.

In the meantime, if you’re supporting del Potro tomorrow against Novak Djokovic, you might consider becoming one of those boorish fans that cheers every first-serve miss off of Novak’s racquet.  Lots of Djokovic second serves might be Delpo’s best path to victory.

London forecast: With Berdych’s win today, all eight players remain in contention.  A lot hinges on Friday’s match between Wawrinka and Ferrer, while we won’t gain much clarity on Group B until tomorrow.

Player     3-0  2-1  1-2  0-3       SF      F      W  
Nadal      70%  30%   0%   0%    98.4%  57.0%  34.1%  
Djokovic   42%  46%  11%   0%    88.3%  54.9%  30.9%  
Ferrer      0%   0%  54%  46%    14.8%   5.5%   2.0%  
Del Potro  22%  50%  28%   0%    71.6%  36.3%  16.4%  
Federer     0%  30%  51%  20%    29.9%  13.1%   5.9%  
Berdych     0%  30%  70%   0%    36.0%  12.4%   4.0%  
Wawrinka    0%  46%  54%   0%    50.9%  17.4%   5.6%  
Gasquet     0%  10%  44%  45%    10.1%   3.2%   1.0%

For the pre-tournament forecast, click here.

Berdych d. Ferrer: Click here for detailed serve, return, and shot-by-shot stats for today’s evening match.


Filed under Serve statistics, World Tour Finals

Roger Federer and the Missing Tiebreaks (+Updated WTForecast)

For most of his career, Roger Federer has been one of the very few players to play better in tiebreaks than in standard deuce games.  His career record, winning breakers at a 65% clip, illustrates his success at the business end of tight sets.  But there’s more to the story.  Even a player a good as Federer has been should not have won that many tiebreaks.

As I wrote in a pair of posts a year ago, there is very little evidence for any kind of tiebreak-specific skill.  Some players do well in tiebreaks, of course, but their success is almost always due to being good in general–better players win more points, and that translates into tiebreaks.  Plenty of big servers, such as Ivo Karlovic and Milos Raonic, don’t win any more tiebreaks that you would expect simply by looking at the rate at which they win points.

However, a tiny fraction of players defy this regression to the tiebreak mean. Playing a ton of tiebreaks seems to help a bit–John Isner always wins more than expected–and a few other cases might be explained by extreme confidence or intimidations.  These include Pete Sampras and–you guessed it–King Roger.

In the eight seasons from 2004 to 2011, Federer won almost 10% more tiebreaks than his stats say he should have.  In 2006, his outrageous 37-14 tiebreak record was a big part of his equally outrageous overall success.  But even a player as good as Roger was that year “should” have only gone 31-20.  That would still have been an impressive win rate, and let’s not forget, many of his tiebreaks were against excellent players who had already pushed him that far.

As with so much else, that tiebreak magic has eluded Fed in the past two seasons.  Last year was the first season since 2003 when he failed to win more tiebreaks than expected.  He has been neutral this year and last.

It’s tempting to wonder, then, how big a part the disappearance of Roger’s tiebreak magic has played in his overall decline.  If he had won tiebreaks at the “extra” rate he did throughout his peak, he would have claimed two, or possibly three more than he actually did, flipping his pedestrian 13-10 tiebreak record to a more Fed-like 15-8 or even 16-7.  (This post was written before Fed’s tiebreak win over Djokovic in London on Tuesday.  In any event, improving his record to 14-10 doesn’t drastically change anything.)

How much of an impact would those bonus tiebreaks have had?  With a bit of guesswork and a handful of counterfactuals, we can put a number on it.  We’re looking at “flipping” two or three of Roger’s ten lost tiebreaks.  Of those ten, three didn’t end up mattering, as he won the match anyway.   The remaining seven occurred in five matches:

The final match in this list provides the simplest illustration of the math involved here.  Flip the lost tiebreak in the Delpo match, and Federer wins the title, earning 200 additional ranking points.  Since we’re only switching the outcome in two or three tiebreaks, that’s either a 20% or 30% chance of that particular tiebreak counting among those switched, for either 40 or 60 additional points.

It gets much more involved with something like the Stakhovsky loss.  Not only do we need to consider the different outcomes of flipping both tiebreaks (and Roger winning) and flipping just one (and Roger maybe winning), we also need to estimate Fed’s chances of progressing through the draw.  Despite the very early loss, Wimbledon was almost double the lost opportunity of any of the other matches, as his path to the semifinal would’ve gone through Jurgen Melzer, Jerzy Janowicz, and Lukasz Kubot.  To quantify the effect of flipping the Wimbledon outcome, we must consider the probability of his reaching those later rounds and the number of points he would have collected had he gotten that far.

Crunch all the numbers, and if you flip two tiebreaks, Federer gains about 380 ranking points.  Flip three, and it’s about 560.  Either of those numbers would move him in front of Berdych in this week’s rankings and given him a lot more breathing room on the road to London.  These bonus points would still have left a huge gap between him and the top five.

Perhaps more important than a few hundred ranking points, how different would the 2013 Federer storyline look if you flipped just a small number of those results?  Give him the 4th set against Stakhovsky and the 2nd with Delbonis, watch him win the deciders, and there’s a different Fed narrative for the summer.  Whether it’s bad luck, decreased confidence, less intimidation, or something else entirely, it’s crucial that we remember that tiebreaks are often decided by a single bad service point or great return point.  If a narrative can’t hold up against a couple of points going the other way, it probably isn’t telling us very much about a player’s actual performance level.

Yet, if Federer has turned a corner this fall, it would be a mistake to expect improved results to come from a resurgence of his tiebreak mojo.  Whatever mysterious factors cause a tiny minority of players to exceed tiebreak expectations, it seems less likely that fading 30-something Fed has them.  He certainly hasn’t benefited from them for the last two years.  But most of all, unless he gets back into more very high-profile matches–as he may this week–the few hundred points he could gain from tiebreak magic just won’t make much of a difference.

London forecast: Today, the results went as expected, with Nadal beating Ferrer and Novak defeating Federer.  Nadal was such a heavy favorite that his win doesn’t affect his chances much, but Djokovic enjoys a bigger bump. The top two seeds are now almost equal, while Federer faces increasingly long odds.

Player     3-0  2-1  1-2  0-3     SF      F      W  
Nadal      50%  42%   9%   0%  91.2%  52.5%  31.5%  
Djokovic   43%  46%  11%   0%  88.5%  54.4%  31.0%  
Ferrer      0%  29%  50%  21%  31.9%  12.2%   4.5%  
Del Potro  22%  50%  28%   0%  71.3%  36.6%  16.7%  
Federer     0%  30%  51%  20%  30.2%  14.1%   6.3%  
Berdych     0%  14%  48%  38%  16.4%   5.7%   2.0%  
Wawrinka   13%  48%  38%   0%  60.5%  21.2%   6.9%  
Gasquet     0%  10%  44%  45%  10.0%   3.3%   1.1%

Click here for the pre-tournament forecast.

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Filed under Tiebreaks, World Tour Finals

Tomas Berdych and Seasons Without Titles (+ Updated WTForecast)

Alone among the eight competitors in London this week, Tomas Berdych has yet to win a title this year.  He reached three finals–in Marseille, Dubai, and Bangkok–but failed each time to close the deal.

This isn’t the first time Berdych has reached the Tour Finals despite lacking a title, either.  In 2010, he finished the year at #6 in the rankings but lost both of the finals he played, at Wimbledon and the Miami Masters.

It isn’t easy to maintain a top-ten ranking without a single tournament win, and Berdych is one of the few players in the recent past to have done so.  In the 23 seasons since 1991, only eleven times have players finished a year in the top ten without a title to their credit, and only three times has a title-less player finished in the top seven.

Twice, a player has finished at #6 without a title (Berdych in 2010 and Tim Henman in 2004), and once, a player has finished at #7 without a title (Jiri Novak in 2002).  If Berdych holds off Roger Federer, Stanislas Wawrinka, and Richard Gasquet this week, he’ll add another season to the list of title-less #6’s.  Unless, of course, he wins in London.

However, winning his first title of the year at the Finals would be far more remarkable than getting this far in 2013 without a championship.  Berdych will be only the sixth player since 1991 to participate in the Tour Finals without a title to his credit, and it wouldn’t take much for him to outperform the previous five.  None of his predecessors–Sergi Bruguera in 1997 (0-2), Novak in 2002 (1-2), David Nalbandian in 2003 (1-2), Henman in 2004 (1-1), and Berdych himself in 2010 (1-2)–have made it out of the round robin stage, winning only four matches among them.

Even if Berdych’s season ends with a poor showing in London, we can still marvel at his ability to rack up points while losing every week.  In the ATP ranking system, winning a late-round match is worth much, much more than an earlier-round contest, so bunching together your successes–reaching finals and winning tournaments–is more valuable than consistently maintaining a decent but lesser level.  Berdych has fallen into that consistent and mediocre category this year, but has done so better than anyone else.

In 22 tournaments this season, the Czech has reached 15 quarterfinals. Only David Ferrer played more quarterfinals this year, though Rafael Nadal (15 of 16), Novak Djokovic (13 of 15), and Andy Murray (9 of 12) reached quarterfinals at a higher rate than Berdych did.

Similarly, Berdych reached eight semifinals, better than everyone except for Nadal (15), Djokovic (11), Ferrer (11), and Juan Martin del Potro (9).  It’s only past this point that he failed, reaching fewer finals than John Isner and as many as the likes of Fabio Fognini and Mikhail Youzhny.

You have to win big matches to make your presence known at the very top of the ATP.  But as the Czech has shown, you can spend years in the bottom half of the top ten without posting many notable victories at all.  For all his talent, Berdych’s status as the forgotten man in London is well-deserved.

With the first two matches in the books, Wawrinka and del Potro are more likely to advance in London this week, while Berdych and Gasquet have tough roads back into contention.  Here is the revised forecast, reflecting Monday results:

Player     3-0  2-1  1-2  0-3     SF      F      W  
Nadal      35%  44%  18%   3%  80.8%  48.1%  30.3%  
Djokovic   25%  45%  26%   5%  70.9%  43.0%  24.6%  
Ferrer      8%  34%  42%  16%  42.4%  16.6%   6.0%  
Del Potro  23%  51%  27%   0%  71.4%  37.7%  17.9%  
Federer    11%  37%  39%  12%  46.9%  22.8%  10.0%  
Berdych     0%  14%  49%  36%  16.5%   6.1%   2.3%  
Wawrinka   14%  49%  38%   0%  60.3%  21.8%   7.5%  
Gasquet     0%  11%  45%  44%  10.8%   3.9%   1.3%

(For comparison, here is the original forecast.)

I charted the Gasquet-del Potro match today, so you can find detailed serve, return, and shot-by-shot stats by clicking here.

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2013 World Tour Finals Forecast

The field for the World Tour Finals next week is set, and the round robin groups are determined.  That allows us to simulate the event, and–using my player ratings–project the outcome.  (My ratings don’t yet incorporate Paris results. David Ferrer and Roger Federer may get mild boosts once their showings this week are considered.)

Obviously, Rafael Nadal is your favorite.  He has a substantial advantage in every category. He’s more likely than any other contender to progress through the round robin stage undefeated, to reach the final four, to play in the title match, and to win the championship.

Not only is Nadal the best player in the field–even on hard courts–but he was also favored by the draw.  For all of Ferrer’s success in Bercy, he is a weaker hard-court player than Juan Martin del Potro, who will play in Novak Djokovic‘s half during the round robin stage.  Federer, despite his decline, is a still more of a hard-court threat than Tomas Berdych–and Nadal drew Berdych.  The only disadvantage in Nadal’s fortunes is represented by Stanislas Wawrinka, who is considerably more dangerous than Richard Gasquet.  As the forecast below shows, Gasquet is very unlikely to be a factor here.

Here is the complete forecast, showing each player’s chances of winning 3, 2, 1, or 0 matches in the round robin, along with reaching the semis, reaching the final, and winning the event:

Player     3-0  2-1  1-2  0-3     SF      F      W  
Nadal      35%  44%  18%   3%  81.0%  49.2%  31.1%  
Djokovic   25%  45%  26%   5%  70.8%  43.0%  25.0%  
Ferrer      8%  34%  42%  16%  42.4%  16.4%   6.0%  
Del Potro  15%  41%  35%   9%  55.9%  29.4%  14.1%  
Federer    11%  37%  39%  12%  48.4%  23.8%  10.7%  
Berdych     7%  32%  43%  18%  39.6%  15.2%   5.4%  
Wawrinka    6%  31%  43%  19%  37.0%  13.7%   4.8%  
Gasquet     4%  22%  45%  29%  24.9%   9.3%   3.1%

As I mentioned above, while Nadal (and, to a lesser extent, the other three members of his group) got the fortunate draw, the impact isn’t that great.  Here is a “draw-neutral” forecast, which randomizes the group assignments with each simulation:

Player        SF      F      W  
Nadal      77.9%  48.4%  30.2%  
Djokovic   74.4%  43.8%  25.7%  
Ferrer     40.6%  16.0%   5.9%  
del Potro  57.3%  30.2%  14.5%  
Federer    50.5%  24.4%  10.6%  
Berdych    37.7%  14.6%   5.3%  
Wawrinka   32.4%  12.4%   4.3%  
Gasquet    29.3%  10.2%   3.4%

The biggest losers in the draw ceremony were Djokovic and Gasquet.  While Novak’s chances of reaching and winning the final are similar, the draw pushed his probability of surviving the round robin stage from 74.4% down to 70.8%.  The odds are against Gasquet in any scenario, but the specific group assignments determined today knocked his chances of surviving the first three matches from 29.3% down to 24.9%.

The good news for Gasquet is that he’s a much, much better eight seed than Janko Tipsarevic was last year.  And with Richie at the end of what may be his career year, it’s that much more likely that anyone in the field of eight could make things interesting this week.

[update: Thanks to Jovan M. for catching some dodgy numbers in the first table. Due to a coding error, I showed each player’s chances of reaching each win total to be too low.  The SF/F/W columns in both tables are unchanged.]

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The Speed of Every Surface, Redux

One of the most popular posts on this blog has been this one, which quantified the speed of every ATP tournament’s surface.  At the very least, it’s time to provide some updated numbers.  Beyond that, we can improve on the methodology and say more about how much we can learn from the numbers.

I was prompted to improve the methodology when I ran an update this week to see how fast the courts are at the O2 Arena in London.  The algorithm, which compares the number of aces (or service points won, or first service points won) to the number we’d expect from those players based on their season average, told me that London is much slower than average–almost 20% below average, on par with Roland Garros and the pre-blue clay Madrid Masters.

Counterintuitive conclusions are fun, but that’s just wrong.

Here’s the problem: Service stats aren’t only affected by servers.  Sure, when Milos Raonic is serving, there will be more aces than when Mikhail Youzhny is serving.  But how many aces Raonic hits is also influenced by the returning skills of the man on the other side of the net.  It’s clear why the algorithm got London so wrong: The eight or nine best players in the world got to where they are (in part, anyway) by getting more balls back.  No matter how fast the court, Mardy Fish wasn’t going to hit as many aces past Jo Wilfried Tsonga or Rafael Nadal in London as he did against Bernard Tomic in Shanghai or Tokyo.

I’ll be more succinct.  The goal is to compare the number of aces on a particular surface to the number of aces we’d expect on a neutral surface.  The number of Expected aces depends on more than just the man serving; it also depends on the man receiving.

(In my article last year, I used three different stats (ace rate, first serve winning percentage, and overall winning percentage on serve) to measure surface speed.  They track each other fairly closely, so there’s not a lot of additional value gained by using more than one.  From here on out, I’m measuring surface speed only by relative ace rate.)

Incorporating more data

To factor in the additional variable, we need each player’s ace rate for the season along with his ace against rate.  With those two numbers, together with the overall ATP average, we can apply the odds ratio method to get a better idea of each match’s expected aces.

For each server in each match, we compare his actual aces to his expected aces, and then take the average of all of those ratios.  The tournament-wide average gives us an estimate of how fast the courts played at that event.

The improved algorithm still insists that aces were 3% lower than on a neutral surface at the 2011 Tour Finals, but counters that with the conclusion that aces were 18% and 8% more than on a neutral surface in 2009 and 2010, respectively.  A weighted average of those three seasons (more on that in a bit) estimates that the O2 Arena gives us 4% more aces than a neutral surface.

The variance from year to year–in some cases, like that of London, suggesting that a surface is faster than average one year, slower than average the next–is a bit worrisome.  At the very least, we can’t simply take a one-year calculation for a single tournament and treat it as the final word, especially when the event only includes 15 matches.

Multi-year averages and (extremely mild) projections

If we want to know exactly what happened in one edition of a tournament, the single-year number is instructive.  Perhaps the weather, or the lighting, was very bad or very good, causing an unusually high or low number of aces.  Just because a tournament’s number for 2012 doesn’t match its numbers for any of the previous three years doesn’t mean it’s wrong.

However, the variety of effects that give us this year-to-year variance do warn us that last year’s number will not accurately predict this year’s number.

The year-to-year correlation of relative ace rate (as I’ve described it above), is not very strong (r = .35).  One way to modestly improve it is to use a three-year weighted average.  A 3/2/1 weighted average of 2011, 2010, and 2009 numbers gives us a better forecast of how the surface will play in the following year (r = .5).

Another way of looking at these more reliable forecasts is that they get closer to isolating the effect of the surface.  As I noted in last year’s article, the weather effects of Hurricane Irene dampened the ace rate at last year’s US Open.  By my new algorithm, the ace rate last year was 7% lower than a neutral surface, while this year it was 5% higher than a neutral surface.  The three-year weighted average would have been able to look past Irene; using data from 2009-11, it estimated that courts in Flushing were exactly neutral.  That not only turned out to be a better projection for 2012 than the -7% of 2011, it also probably better described the influence of the court surface, as separate from the weather conditions.

Below the jump, find the complete list of all tour-level events that have been played in 2011 and/or 2012.  The first four numerical columns show the relative ace rate for each year from 2009 to 2012.  For instance, in Costa Do Sauipe this year, there were a staggering 61% more aces than expected.  The final two columns show the weighted averages for 2011 and 2012.  Each event’s “2012 Wgt” is my best estimate of the current state of the surface and how it will play next year.

I’ve also created a prettier, sortable version of the same table.

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The 2012 World Tour Finals Forecast

With Jo Wilfried Tsonga‘s win last night over Nicolas Almagro, the field is set for the tour finals.  Novak Djokovic and Roger Federer will each head one of the two round robin groups, and will be joined by Andy Murray, David Ferrer, Tomas Berdych, Juan Martin Del Potro, Tsonga, and Janko Tipsarevic.

Despite Federer’s dominance on indoor hard courts last year, he is hardly the same unstoppable force this season.  Not only did he lose in last week’s final to Del Potro, but my rating algorithm, Jrank, views him as a slightly inferior hard-court player to Murray.  Though it will certainly be close, my forecast favors both the Serb and the Brit over the soon-to-be world #2:

Player         SF      F      W  
Djokovic    77.7%  47.7%  28.8%  
Murray      70.0%  41.9%  23.3%  
Federer     72.6%  40.4%  22.3%  
Del Potro   45.9%  20.2%   8.3%  
Ferrer      45.4%  17.7%   6.5%  
Berdych     38.8%  15.2%   5.5%  
Tsonga      30.4%  11.3%   3.8%  
Tipsarevic  19.2%   5.5%   1.5%

As always, there are as many reasons to question these numbers as there are to put one’s faith in them.  Djokovic’s loss to Sam Querrey this week seriously questions his current ability to play his best tennis.  Murray’s loss to rising star Jerzy Janowicz isn’t quite so troubling, but it also fails to fit the profile of a dominant player.

In the bottom half of the pack, one or two of these guys are likely to play in the Paris final, meaning they’ll be relatively tired upon arrival in London.  It’s one thing to play the first round of a tournament on weak legs; it’s another when that event is the Tour Finals and your first opponent is a fellow top-tenner.

[UPDATE, 3 Nov]

The draw is set.  Federer is joined in Group B with Ferrer, Del Potro, and Tipsarevic, leaving Djokovic with Murray, Berdych, and Tsonga.  This is a dream setup for Federer, and even dreamier for Delpo.

Federer’s career H2H against the three men in his group is 31-3.  His career H2H against Novak’s opponents is 27-18.  He might prefer not to face Del Potro again so soon, but historically, the Argentine hasn’t been any more dangerous for Roger than any of the three men Djokovic will have to face.

As noted, it’s the absolute perfect draw for Delpo, too.  Statistically, Federer is weaker than Djokovic.  My numbers might overstate Ferrer’s competitiveness in London (and they still aren’t very high), and Tipsarevic is essentially a non-factor.  In the pre-draw simulation above, Del Potro has a 45.9% chance of reaching the semis and a 8.3% chance of winning it all.  Post-draw, 54.4% and 9.2%.  It’s an uphill battle no matter what the draw, but avoiding the Murray group is a huge help.

Here are the projections, now reflecting the draw:

Player         SF      F      W  
Djokovic    74.0%  47.2%  28.2%  
Federer     76.7%  41.2%  23.0%  
Murray      68.5%  41.6%  22.6%  
Del Potro   54.4%  22.4%   9.2%  
Ferrer      46.9%  17.9%   6.8%  
Berdych     31.2%  13.5%   5.0%  
Tsonga      26.3%  10.4%   3.6%  
Tipsarevic  22.1%   5.8%   1.6%

Thanks to his relatively weak round-robin group, Federer has the best shot at reaching the semis, but only the third best chance of reaching the final, since he’s likely to face either Djokovic or Murray in his semi.  Despite the tougher draw, Djokovic remains the favorite to win the event and put an exclamation point on his season-ending #1 ranking.

(A quick programming note for regular readers: I won’t be able to update these predictions throughout the tournament on, and due to an uncooperative travel schedule, the next update (including Bercy results) may not occur until Tuesday or Wednesday.)

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