Category Archives: Juan Martin Del Potro

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 Juan Martin Del Potro, Serve statistics, World Tour Finals

Lopsided Four-Setters, Orderly Doubles, and Sock’s Luck

On Wednesday, Guillermo Garcia-Lopez appeared to give Juan Martin del Potro quite the battle, taking him to four sets, with two tiebreaks along the way.  It wasn’t what anyone expected from Delpo’s first-round match against someone ranked outside the top 70.

Looking behind the scoreline, however, it becomes evident that the Argentine dominated the match.  Frequent HT commenter Tom Welsh pointed out that del Potro’s Dominance Ratio (DR) was 1.64, a mark that Delpo had not reached in his previous nine matches, and not since posting a 1.68 DR in a routine victory against Bernard Tomic in Washington.

Of course, a stat like DR, which considers the total number of return points won and service points lost, will not capture the ups and downs within a match..  What it does tell you is, over the course of the afternoon, how well both guys were playing.  And comparatively speaking, del Potro was playing much better.

Delpo had previously played 29 matches in his career in which he finished with a DR between 1.6 and 1.7, and in all but one of those (a three-setter against Dudi Sela in Washington in 2008) he won in straight sets.

It turns out, though, that in Grand Slam play, dropping a set in the middle of an otherwise routine performance–as measured by DR–isn’t that uncommon.  While the average DR in a Slam four-setter is only 1.37, the winner has tallied a DR of 1.64 or better in more than 12% of Slam matches since 1991.

If there’s a takeaway here, it’s something we should already know.  In a tennis match-especially one with tiebreaks–some points are tremendously more important than others.  Garcia-Lopez saved 9 of 13 break points.  Take away one of those in the second set, and we’re not having this discussion.  Give Delpo one more of the first 12 points in the second-set tiebreak, and things could’ve turned out differently.  One well-timed, high-leverage point has the potential to overturn dozens of points worth of poor play.

Yesterday I mused on the chaos that is men’s doubles, and the Bryan brothers’ ability to rise above it.  Yesterday’s action was surprisingly unchaotic.

By the end of play yesterday, 15 of the 16 men’s doubles seeds had completed their first-round matches.  (Sixth seeds Edouard Roger-Vasselin and Rohan Bopanna play today.)  Of those 15, 10 reached the second round, including every top-seven seed who has played.

Compare that to men’s singles, in which 10 of 32 seeds crashed out in the first round.  For a more direct comparison, consider that 4 of the top 16 men’s singles seeds lost in the first-round.  Arguably, the doubles players have a tougher task.  Since the field is made up of only 64 teams, the first round can be more challenging in doubles than in singles.

What makes the sticking power of these top seeds surprising is the number of good doubles players who aren’t part of seeded teams.  Because the game is less physically demanding, doubles specialists can play on to much more advanced ages than can singles players.  One of the teams that executed an upset yesterday, Jonathan Erlich and Andy Ram, was in 2008 ranked among the top few pairings in the world.  Further, plenty of singles players have proven themselves quite adept at doubles, but don’t play enough to amass much of a ranking.

Part of the reason why the seeds have progressed more-or-less intact is the US Open format of three full sets.  At other levels, the third-set match tiebreak essentially turns the contest into a coin flip.  Both the second- and fifth-seeded pairs were forced into a third set, and at an event with a ten-point tiebreak, the odds would’ve been much higher that one of them would be headed home.

Jack Sock is playing only his fifth Grand Slam, and his first as a direct entry, having recently gotten his ranking into the top 100.  Part of the reason he was able to move into that rarefied air is his lucky path to the third round in last year’s US Open.

In 2012, his first-round draw was Florian Mayer, who retired in the middle of the third set.  That gave him a shot at the relatively weak Flavio Cipolla, who he beat in straight sets.  He gave Nicolas Almagro a scare in the third round but ultimately lost.  Still, he took home 90 ranking points instead of the 10 he would’ve collected had he lost to a healthy Mayer in the first round.

Defending those points, one might expect the young American to take a tumble in the rankings after the US Open.  After all, your typical 86th-ranked player doesn’t have much chance to reach the third round, let alone do so two years in a row.

But fortune has favored him again.  In the first round, he drew Philipp Petzschner, who retired in the middle of the third set.  (Sound familiar?)  Yesterday, he defeated the clay-court specialist qualifier Maximo Gonzalez, who did him the huge favor of knocking out Jerzy Janowicz in the first round.

It’s hard to imagine an easier route to a Slam round of 32.

You may have noticed the string of three-set matches contested by Petra Kvitova, earning her the moniker “P3tra.”  Amy Fetherolf takes a closer look at The Changeover, finding that Kvitova’s season is every bit as unusual as it seems.

At his site Betting Market Analytics, Michael Beuoy shows us the trajectory of Vicky Duval’s historic first-round upset, similar to some of the win-probability work I’ve done in the past.

Finally, more Duval: I charted her match last night, and have reams of data to show for it.


Filed under Doubles, Jack Sock, Juan Martin Del Potro

Raonic, del Potro, and the Importance of One Point

In last night’s Coupe Rogers match between Milos Raonic and Juan Martin del Potro, one point stands out from the rest.

Raonic won the first set, then Delpo broke early in the second.  With del Potro serving at 4-3, Raonic earned a break point with a winner at the net.  Replays clearly show that he touched the net.  Had the chair umpire seen it in real time, Delpo would have been awarded the point.

The Argentine never recovered, losing the next nine points and the match.

The net touch, and the point Milos didn’t deserve, was clearly a turning point in the match.  But how important was it, really?

If we assume that the two men were equal and that both players win 75% of service points (not true in Delpo’s case yesterday, but reasonable for two big servers on hard courts), here is a summary of Raonic’s probability of winning at various stages of the match:

  • After winning the first set: 75.0%
  • With Delpo serving 4-3, 00-00: 52.4%
  • With Delpo serving 4-3, 40-40: 53.9%
  • After winning the “touch” point: 58.9%
  • If Delpo had won that point: 51.8%
  • After winning the “touch” game: 75.0%
  • After holding serve for 5-4: 76.3%

The controversial point was, clearly, very important.  The difference between winning it and losing it was 7%, a magnitude that doesn’t happen very often in a tennis match, especially outside of tiebreaks.

But the real story here is the next point.  Remember that under normal circumstances, del Potro is a huge server and Raonic does not have a strong return of serve.  (I say “normal circumstances” because somehow, Raonic won 50% of return points in this match.)

If a server is winning 75% of points on his own racquet, his probability of winning a game from break point down is still 67.5%.  There’s a 25% chance he’ll lose the game on the next point, of course, but a 75% chance he’ll get back to deuce, where his serve gives him a 90% chance of winning the game.

The touch point increased Raonic’s chances of winning from 53.9% to 58.9%.  The next point upped his odds from 58.9% to 75.0%.  Which one do you think was more important?

Another way of looking at this to consider what would’ve happened had there been no video replay, and no chance of del Potro spotting the touch and arguing with the umpire about it.  Normal Delpo would’ve stepped back to the line and hit a service winner.  Five minutes later he would’ve held serve again and the two men would’ve played a third set.

It’s easy to look back at this match and conclude that the net touch was the difference in the match.  But no: It was the reaction to the touch–the controversy itself–that had a much greater impact.


Filed under Juan Martin Del Potro, Milos Raonic, Win probability

Known Unknowns for Rafael Nadal

When Rafael Nadal returns to the tour–very soon, we hope–he will be entering uncharted territory.  Plenty of players miss time to injury, but it is rare for a top player to miss anywhere near this much time.

In fact, only three top 10-ranked players have ever left the tour and returned after a layoff of six months or longer.

Only one of those three–Juan Martin del Potro, in 2010–was forced to rest due to injury.  John McEnroe twice left the tour for stretches of several months, and Tommy Haas took time off in 2002 to take care of his family.  Haas’s layoff turned into something a bit more relevant, as his sabbatical was extended by a shoulder injury he suffered in preparation for a comeback.

While del Potro’s future is still unclear, the precedent for Nadal is concerning.  None of those players ever returned to their pre-layoff rankings.

Del Potro’s story, in fact, is the most encouraging.  When he suffered his shoulder injury, he had recently won the US Open and reached the final of the World Tour Finals, reaching a career-high ranking of #5.  With the exception of a brief return in October of 2010, he missed almost exactly one year.  While he didn’t return to the top 10 for another year, he won two small tournaments early on and reached the semifinals of Indian Wells barely two months into his comeback.  Two years later, his ranking is up to #7, still short of his pre-injury peak.

When Haas left the tour at the end of 2002, he had just recently fallen from his career-high ranking of #2.  When he returned more than a year later, he had early success similar to Del Potro’s, reaching the 4th round at Indian Wells and winning two events in his first six months.  Yet he didn’t return to the top 10 for nearly three years.

McEnroe is the enigma of this bunch.  Ranked #2 in the world at the beginning of 1986, he needed a break from the tour.  Seven months later, he began a comeback at Stratton Mountain, where he reached the semis and lost to Boris Becker.  After a clunker of a first-round loss at the US Open, he reeled off 18 consecutive wins, including three over top-10 players.  That put him back in the top 10, but it was two years into the comeback that he regained a position in the top 5–in part due to another six-month layoff beginning in September 1987.

Aging patterns

What the recaps of Haas’s and McEnroe’s layoffs hide is that, while they weren’t playing, they were headed into an age range where most pros start declining.  At the time of their returns, McEnroe was 26, Haas 25–a typical player’s peak age, at least before today’s new era of indestructible 30-somethings.

While McEnroe has shown astonishing longevity, his years as a contender for world #1 were probably about over when he took his sabbaticals.  And Haas missed the year in which he might have played his very best tennis.

Neither player is a clear precedent for a clay court genius with knee problems, but the age factor is tough to ignore.  Nadal turned 26 in June, putting him right in between Haas and McEnroe at the times of their departures from the tour.

Assuming Rafa is healthy, there’s little doubt he’ll maintain his position in the top 10.  I’d be surprised if he didn’t win at least a couple of clay court events this year, even if he maintains a much-reduced schedule.  But if history is any indication, he has seen the last of the top two.


Filed under Injuries, Juan Martin Del Potro, Rafael Nadal, Tommy Haas

The Most Familiar Faces

In last week’s Basel final, Roger Federer and Juan Martin Del Potro faced off for the seventh time this year, and the 16th time overall.  Seven times in one year is an awful lot, about 10% of Delpo’s matches.  It’s even more remarkable because only two of those contests have been finals — in order to meet so many times, the draws of several tournaments had to complement their consistently strong play.

Making matters even more extreme is that there is a better-than-50% chance that Federer and Del Potro will meet in London next week, bringing the total to 8.  And there’s a slim chance–if they are drawn in the same group, then play again in the final–that the sum will reach 9.

So, what’s the record?  Seven is already pretty good, right?

Single year head-to-heads

In fact, as with so many other records, Federer is #1 in the last 30 years.  He holds the record with Jo Wilfried Tsonga, against whom he played eight times last year.  (In the entire professional era, the mark belongs to Ilie Nastase and Tom Gorman, who played at least nine times in 1972.  I’ve excluded years before 1980 because a variety of factors caused the top players to meet much more frequently than they do these days.)

As long as Fed and Delpo are at seven, they will be tied with four other pairs: John McEnroe and Ivan Lendl in 1984, Jim Courier and Michael Chang in 1995, Novak Djokovic and Rafael Nadal in 2007, and Novak/Rafa again in 2009.  Another 11 pairs met six times in a single year, including Nadal and Djokovic in 2008 and 2011.  (Along with, weirdly, Rajeev Ram and Donald Young in 2007.  Must be the wild cards.)

All-time head-to-heads

Since Djokovic and Nadal show up at the top of the single-year list no more than four times, it stands to reason that they must be near the top of the all-time list, as well.  Indeed, they are.

In fact, assuming Nadal returns to health in anywhere near his historical form, this current pair of stars will almost undoubtedly take over the all-time lead next year.  They could hold it for a very long time.

Player 1       Player 2        H2Hs    W-L  
Ivan Lendl     John McEnroe      35  20-15  
Ivan Lendl     Jimmy Connors     34  22-12  
Pete Sampras   Andre Agassi      34  20-14  
John McEnroe   Jimmy Connors     34  20-14  
Rafael Nadal   Novak Djokovic    33  19-14  
Boris Becker   Stefan Edberg     32  22-10  
Roger Federer  Novak Djokovic    28  16-12  
Rafael Nadal   Roger Federer     28  18-10  
Stefan Edberg  Ivan Lendl        26  14-12  
Roger Federer  Lleyton Hewitt    26   18-8

This is one record that, for all of his dominance, Federer will probably never co-hold.  To find yourself on this list, you not only need to rank among the all-time greats, you need a very-near-contemporary who ranks just as high.

(If you’re interested in head-to-head records, I hope you’re already using the Head-to-Head Matrix on  It’s updated every week, and shows the career H2H records of every matchup within the current top 15.  Each H2H record is linked directly to a listing of the relevant matches.)


Filed under Head-to-Heads, Juan Martin Del Potro, Records, Roger Federer