The Unaceables

Last night, Florian Mayer solved the John Isner serve, breaking the American three times en route to a straight-set victory.  Mayer is known as a tricky opponent, but not as a particularly good returner.  He had never played Isner before, though he beat Ivo Karlovic in Miami last year.

One element of his success is that he got his racquet on the Isner serve.  Over the last 52 weeks, Isner has amassed a 17.1% ace rate, meaning that about one in six of his serves are untouchable.  Last night, he barely managed 10%, as Mayer allowed him only six aces.

We might wonder: Is this is a skill of Mayer’s that we’ve failed to notice before?  At first glance, it doesn’t appear to be.  While Mayer often holds his opponents to low ace numbers, he’s had some horrible performances in that department, allowing Feliciano Lopez a 20.4% ace rate in Shanghai last year, Thomaz Bellucci 15.5% in Madrid on clay, and while playing injured, he ignominiously allowed Ivo Karlovic a 50% ace rate at last year’s Cincinnati Masters.

We can answer this question not just for Mayer, but for every regular on the ATP tour.  While some servers hit far more aces than others, ace rate is influenced by both the server and the returner.  Mayer himself is a good example.  In the last 52 weeks, he’s had eight matches in which at least one in ten serves went for an ace.  But in five other matches, he didn’t hit a single one!  Some of the variation is due to good and bad serving performances, but a substantial part can be explained by the man on the other side of the net.

As  it turns out, last night was an aberration for the German.  Mayer is below-average at ace prevention, allowing 8% more aces than an average player, ranking 80th among the 139 active players whose results I analyzed.

I looked at every 2011 and 2012 match, using only those matches in which both players racked up 10 matches in the last fifteen months.  After calculating each player’s ace rate, I generated an “expected” number of aces for each returner.  Simply tallying how many aces a player allowed isn’t good enough–this way, we adjust for the quality of the server.

Mayer, for instance, played 70 matches in that span against opponents who also played at least 10 matches.  (I excluded guys who played fewer than 10 because their ace rate in such a small number of matches may say more about their opponents than themselves.)  In his 4812 return points, he allowed 345 aces.  But based on the serving abilities of his opponents, he should have allowed only 321.  Those numbers will look a little better after last night, but not enough to move him up very much in the rankings.

By contrast, the best returners get their racquets on just about everything.  Atop the list is Gael Monfils, who allows barely half the aces that we would expect him to.  The top eight returners all reduce expected ace rates by at least a third.

In the table below, I’ve shown these stats for the ten players who appear to be the best at avoiding aces, along with 20 other players of interest.

Player                 Rank  Matches  vAce%  expAce%    Diff  
Gael Monfils              1       62   3.5%     6.8%    -48%  
Benoit Paire              2       23   3.8%     6.3%    -40%  
Andy Murray               3       81   4.4%     7.3%    -39%  
Stanislas Wawrinka        4       61   4.2%     7.0%    -39%  
Cedrik Marcel Stebe       5       12   3.2%     5.2%    -38%  
Viktor Troicki            6       70   4.3%     7.0%    -38%  
Gilles Simon              7       77   4.7%     7.3%    -36%  
David Ferrer              8       90   5.1%     7.8%    -35%  
Carlos Berlocq            9       53   4.7%     7.0%    -32%  
Mardy Fish               10       71   5.7%     8.3%    -31%  

Jo Wilfried Tsonga       14       89   5.7%     7.9%    -28%  
Roger Federer            20       92   6.0%     7.9%    -24%  
Novak Djokovic           22       89   6.4%     8.4%    -24%  
Kei Nishikori            32       63   5.8%     7.0%    -17%  
Rafael Nadal             34       91   7.4%     8.8%    -16%  
Nikolay Davydenko        38       60   5.8%     6.7%    -14%  
Sam Querrey              39       35   6.7%     7.8%    -14%  
Milos Raonic             40       60   6.7%     7.6%    -12%  
Kevin Anderson           53       74   7.5%     8.0%     -6%  
John Isner               59       68   7.6%     7.8%     -2%  

Radek Stepanek           73       62   8.6%     8.0%      6%  
Lukasz Kubot             74       44   8.5%     8.0%      7%  
Ivo Karlovic             78       45   7.9%     7.3%      7%  
Juan Martin Del Potro    81       84   8.8%     8.1%      9%  
Tomas Berdych            91       87   8.5%     7.6%     12%  
David Nalbandian        102       43   9.4%     7.9%     20%  
Arnaud Clement          120       17   9.3%     7.2%     29%  
Andy Roddick            130       55  11.8%     8.3%     42%  
Bernard Tomic           135       38  12.8%     8.5%     50%  
Olivier Rochus          139       36  14.7%     7.2%    103%

Before we go anointing Monfils and Benoit Paire the greatest returners in the game, it’s important to remember the serious limitations of the ace stat.  Much more important is getting the return in play.  But except for Grand Slam matches, we don’t have those numbers. In the meantime, we can use ace rate and return points won as proxies for return skills.

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2 Comments

Filed under Research, Return stats

2 responses to “The Unaceables

  1. Do you control for the surface that matches are taking place on? Presumably people who play more matches on clay for instance would be likely to prevent more aces than those who play more of their matches on quicker/more server friendly surfaces.

    • They don’t adjust for surface. But surface is partially accounted for by adjusting for opponent, since players who play a lot of clay mostly play other guys who play a lot on clay. (say that ten times fast!)

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