🎾 Pt 2 - What happens at different levels of the competitive ladder — and how a player's skills shape the structure of a match.

This is the second in a series on differences in how tennis matches play out at different levels of the sport. I compare women’s and men’s recreational matches, Division 1 college matches, International Tennis Federation events, and WTA/ATP tour level events. Data can tell great stories: here’s one of them.

Serve Dynamics: Risk and Reward

At every level, the serve is tennis’s first and most direct test of a player’s skill level. It is also a balance of risk versus reward. These data show how differently men and women at different levels are able to achieve at that balance. While the trends for men and women are similar, they are worth taking in turn.

As a quick reminder from the start of this series, here is how women’s and men’s points end on average for different levels of tennis:

For women, the share of double faults to other point outcomes are noticeably fewer at each stage from recreational to college to professional levels, by nearly half from a recreational game compared to the WTA tour. Let’s say once again that a match consists of 100 points. The average 3.5 - 4.0 woman hits about 5.6 double faults in that match, while the average WTA player hits around 4.8. It’s not too surprising that serves are better in this way. But the share of outright service winners and aces follows a slightly different pattern. Those point outcomes through the college level are less than the recreational level before rebounding at the pro level. 

Women
	Rec 3.5 and 4.0	Rec - all	D1	ITF	WTA
Unreturn-ables per game	1.13	1.00	0.75	1.05	1.20
Serve Strength per game	0.70	0.58	0.59	0.70	0.88

As shown above, the number of unreturnable serves per service game are a third fewer from the 3.5/4.0 level to D1, or just over 1 per service game compared to less than 1. Unreturnable serves then rebound, by over 60%, from the D1 to WTA level. Unreturnables once again appear about once per service game.

But, factoring in reduced double faults (serve strength in this table are aces, plus other unreturnables, minus double faults), women in WTA matches are serving 25% better than the 3.5/4.0 recreational matches…and show me someone who doesn’t want to serve 25% better! This represents a dramatic efficiency gain, and one that persists even after accounting for the fact that WTA matches include nearly one additional point per game on average.

It appears that only after college does the average women’s serve (and risk tolerance) improve so much that it has the ability to overpower returners (and we’ll come back to this point when looking at rally length).

For men, the transformation is even starker. Double faults are dramatically fewer, from 9% of every 100 rally outcomes (or points) to less than 4%. Aces, however, move from fewer than 3% of points to more than 8%. The percentage of points ending with service winners, not including aces, are fewer from rec to D1 matches–likely reflecting both stronger returns at the D1 level as well as some of those service winners turning into outright aces as power and need for higher risk tolerance grow in college.

Men
	Rec 3.5 and 4.0	Rec - all	D1	ITF	ATP
Unreturn-ables per game	1.14	1.09	0.91	1.28	1.60
Serve Strength per game	0.68	0.70	0.68	1.05	1.37

From 3.5/4.0 recreational matches compared to the ATP, unreturnables are slightly fewer through D1 matches and then climb dramatically, a 44 percent difference overall. And when adjusted for the smaller share of double faults, serve strength is more than double! 

That trajectory underscores how professional men exploit serve power and risk (for more on this point, see THIS great blog post from a few years ago about serving risk and reward). It also underscores that while unreturnables are at least in part determined by the ability of the returner, double faults are the only shot completely within the control of the server, as we see those falling reliably from one level to the next.

Across both sexes, the serve becomes more of a weapon–as we would guess as accuracy and power increase with better form. The percentage of service points won for both women and men  is around 50% for recreational and D1 matches, but it is around 57% (women) and 64% (men) for professional matches. But, the returners’ skill and power make it necessary to go for higher-risk serves at the pro level.