Second Serves: Where Game Theory Goes Out the Window

The Second Serve Paradox

Across nearly every level of tennis that we’ve studied at Next Level Stats via an exceptional dataset made available by SwingVision, one pattern refuses to disappear: servers overwhelmingly favor hitting to the returner’s left side, which usually means returners are forced into a backhand shot. 

This tendency shows up on most serves, but it becomes especially pronounced on second serves, when pressure rises and margin matters most. (note: earlier research actually shows that servers at the junior level are hitting body serves, but to allow some of the tests we’re running we only split the service box into left and right).

This isn’t rocket science–most players have a weaker backhand. But what’s really striking in this data is that the same tactic produces very different probabilities of winning a second serve depending on the level of play.

Persistence Without Payoff

Let’s take second serves to the deuce court for recreational men and women as an example. Both groups send just over half of their second serves to the returner’s left. But while the payoff for hitting to either side of the service box is basically equal for men (both rounding to 42%), for recreational women second serves to the left on the deuce side win the point only 39% of the time compared to 46% of second serves to the right. That’s huge (and is indeed statistically significant)!

This demonstrates pretty conclusively that hitting more serves wide to the deuce court would benefit most recreational women compared to targeting their opponent’s backhand as often. In other words, many recreational players are repeating a pattern that only feels safe without actually helping them win points. Ladies: try this out. Please! You’re losing most of these points either way, so what do you have to lose?!?

When the Same Bias Works

Now let’s contrast that with college tennis. D1 men and women show an even stronger tendency to serve to the left on second serves—especially on the ad court. Look again at the figure above. Where is that men’s college player hitting on his next ad court second serve? I’ll tell you where. To the returner’s left…67% of the time!

But here’s the key difference: at the college level, those left-side second serves are often more effective via spin, speed, or otherwise. Win probabilities to a returner’s left are just slightly higher than to the right for men (47% v 46%), suggesting that players are exploiting real return-side weaknesses rather than defaulting to comfort.

Now the real kicker. D1 women show the same second serve tendency on the ad court (slightly less pronounced than men actually). But once again they would benefit from being more balanced in their serve direction. Serves to the returners right (down the T) on the ad court result in a point won 46% of the time versus 41%. 

This was not statistically significant, but was still a strong enough result that we’d encourage D1 women to test this theory out in match play. Hit one or two more down the T on ad court second serves and let us know how it works out (seriously just one or two–there are only about 10 of these per match for each player).

Why Second Serves Break Game Theory

These are just a few examples of where mental pressure likely pushes players toward “safe” patterns rather than winning ones. For decades, this kept NFL coaches from going for it on 4th down. And recent research shows that it might also be keeping penalty kickers from shooting to the most advantageous spots in high-pressure situations. But we need to normalize analytical thinking in tennis just as much.

If you’re hitting 55–60% of second serves to one location and not winning more points there, you’re giving your opponent free points. You need to start measuring your serve tendencies to find out if this is you.