Saturday, January 21, 2012

So Long Second Serve?

Traditionally when playing tennis, players will hit their first serve harder and flatter and closer to the lines than their second serves.  This causes a lower percentage of first serves to go in the box, but a higher winning percentage when they do.  Second serves, with less speed, more spin and a higher margin of safety go in more often, but the server wins a lower percentage of those points.  So far so good.

I was watching Ivo Karlovic play Roger Federer in the 2012 Australian Open the other night.  Ivo was struggling to win points on his second serve, but was serving a high percentage of first serves.  Since Ivo is 6'10" tall, his serve is awesome and he was winning a high percentage of points when his first serve was in the box.  Both players held serve until a first set tie-break.  Ivo got himself a set point, serving at 6-5 in the tie-breaker.  He missed his first serve.  Uh oh.  I'd been telling my wife for half an hour that he should be bombing second serves, and at set point I was yelling at my TV.  "Bring it, Ivo!!!  Pound the second serve!".  He spun it in, lost a flukey point.  Lost the set and the match.

Odds are Ivo would have lost the match no matter what he did on that point.  Federer is better than Ivo Karlovic.  However, Ivo would have given himself a better chance to win on this occasion if he had hit two "first serves" rather than a first and a second serve.  The data for this match are obvious, but what's interesting is the data for the tournament so far indicate that the strategy of hitting two first serves may become the norm in men's tennis in the not-too-distant future.

Here are the stats for Dr. Ivo against Federer.  Ivo made 71% of his first serves (ave speed 123 mph) for a winning percentage of 76% on first serve.  Ivo made 71% of his second serves (ave speed of 105 mph) for a winning percentage of 34%.  It should be obvious from those stats why hitting two bombs was a better idea for Ivo than spinning in a second serve, if you can call hitting it 105 mph spinning it in!  Ivo missed way too many of his second serves.  Typically ATP tour pros make 95% or more of their second serves.  Perhaps under pressure from Federer, Ivo made a woeful 71% of his second serves, the same as his much harder first serve.  So by abandoning the losing slower serve, Ivo would have increased his winning percentage on serve from 62% to 74%.  That's a dramatic increase in his chances of holding serve.

As I said, that case was easy because of Dr. Ivo's tragic second serve percentage and woeful winning percentage on second serve.  But what about for the field in general?

Here are the first round stats (the second two rounds are similar, but with fewer data points).  The men made 61% of their first serves and won 69% of those points.  They made 96% of their second serves and won 49% of those points.  The result of all that is that servers won 61% of their points using the traditional "hard first, spin second" serving strategy.

What would the numbers look like if the men had hit "hard" serves for both first and second serves?  They would have won 58.5% of their service points.  So in aggregate, for now, the traditional serving strategy is the better one by 61% to 58.5%.

My guess is that as players get taller and returners continue to get better, that gap will vanish for everyone like it vanished for Dr. Ivo.

If that gap does vanish and men hit two bombs, if necessary, on each point, the enjoyment level of men's tennis will fall dramatically.  We'll be back to the days of Sampras vs Ivanisevic at Wimbledon.  Yawn.  Let's hope that doesn't happen.

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