Bruin Sports Analytics
Success and Aggression on the Serve
By: Chinmay Varshneya and Leo Cardozo
There’s only one stroke in tennis which a player can entirely control, the serve. With the serve, players have the ability to finish a point without hitting another shot. As a result, being on serve poses a tremendous advantage, as the average professional servers hold serve between 75 to 80 percent of the time. A unique aspect of the serve is that players are allowed two tries. For lower level players, the focus of a second serve is simply to tap the ball in, no matter how weak it is. However, at the higher levels, the second serve is converted into a tactical shot where players balance speed and large amounts of spin to give the serve a higher margin of error. On the ATP Tour, the highest level of professional tennis, most players use a kick serve (involving topspin) on this shot. This leads to an average second serve speed of around 151.5 km/hr for all players, roughly 50 km/hr slower than first serves. But players still have the choice to hit their second serve as hard as they want. If we consider a small group of (very tall) elite servers like Reily Opelka and John Isner, second serves can reach an average speed just shy of 200 km/hr. While an often cited major component of both first and second serve speed is a player’s height, on the second serve, players intentionally dial down power and aggression to ensure a greater chance of making the shot. This creates an obvious trade off, as a slower serve is easier for the opponent to attack and ultimately gives them better odds of winning the point. This article will study that trade off and analyze the relationship between serve make percentage and speed. We will also try to determine which players would benefit most from increasing their shot aggression on their second serves, as well as serves in general.
Analyzing the Relationship Between Serve Speed and Double Faults
This first graph demonstrates the relationship that serving harder makes your serve less likely to go in, which most players intuitively understand. Although the R-squared of this relationship is only around 0.13, the p-value for serve speed is under 0.0001, suggesting that harder serves do contribute to an increased double fault rate. One explanation for this is because when one serves faster, they have less room for error and are thus more likely to miss. It is important to point out however, that this is not exactly equivalent to racket head speed or how hard a player swings at the ball. If a player takes a swing path that is more tangential to the ball to impart greater spin, the racket head speed will more so translate to an increase in RPM rather than km/hr. Therefore, the y-axis is also some indication of how much a player flattens the ball out on the serve.
Which Players Should Be More Aggressive on Second Serves?
One approach to understand how players could increase the effectiveness of their second serve is to see how they would fare if they maximized aggression. The above graphic demonstrates how successful players would be if they took a high risk high reward approach and hit two first serves instead of a second serve. In order to do this, we are multiplying first serve make percentage by first serve win percentage and comparing this to second serve win percentage. The blue dotted line represents the breakeven point, where players would win more points from hitting two first serves. As you can see, while most players would actually lose more points with a two first serve approach, there are a couple of notable exceptions in John Isner and Nicolas Jerry.
Nicolas Jarry is known for having quite an unconventional service motion where he holds the racket above his head before he tosses the ball. This results in a more simplified and abbreviated motion, which likely contributes to his very high first serve make percentage of around 80. It is also worth noting that he is on the taller end of tennis players at 6’6. Next is Isner, who is generally recognized as the best (active) server in tennis amongst his peers. This is likely in large part due to his height. The 6’10 American is the second tallest player on the ATP tour at the moment. Other players such as Daniil Medvedev and Alexander Zverev, who are both 6 '6 are also known to start hitting two first serves when they are in a serving rhythm or playing against exceptionally strong returners. While from this data it is hard to recommend that most players begin hitting two first serves, some players with extremely effective first serves could benefit from increasing second serve aggressiveness.
Which Players Should Be More Aggressive on First Serves?
The graph above can help indicate which players are not being aggressive enough on their first serves. In general, one can observe a positive correlation between the percent of first serves made and the percent of points won. However, there are some players, located in the fourth quadrant, who despite being in the higher percentiles of first serves made are actually below the 50th percentile in points won. While their serves may not be as powerful as the taller players mentioned above, out of necessity, it might make sense for them to begin sacrificing some of their excess make percentage for increased speed and aggression because as it is, their serve consistently is not translating into points won. It is also worth noting that this graph shows first serve percentage, meaning that if these players began hitting far riskier serves, even if they missed more, they would still have a second serve to fall back on.
One noteworthy member of the bottom right quadrant is former Bruin and NCAA Champion, Marcus Giron. His scaled percentage of first serves made is 0.5419 indicating a high level of consistency. Despite this, when it comes to first serve points actually won, his scaled percentage sits at 0.3697, which is below average. It is worth noting that he plays very well from the baseline, indicating he has strong groundstrokes. The now 8-year ATP veteran, should therefore invest in taking more risks on his first serve when it comes to speed and placement. By emphasizing a more aggressive first serve in order to win points outright, he is likely to have an easier time holding serve which will translate into better match outcomes.
Overall, the majority of players are making the right decisions on their serves, maximizing speed while limiting the amount of free points given away to double faults. But, as we discovered today, there are still room for improvement among some players, with extremely effective servers having reason to serve harder on second serves, and less effective ones incentivized to try and steal more points on their first serve.
Our analysis focuses on players on the ATP tour, but we aim to look into players on the WTA tour in the future. In addition, analyzing other variables that go into the serve in addition to speed could help understand serve effectiveness.