In tennis, the speed of the serve has been measured for decades. It usually flashes right after the serve either directly on the scoreboard, or on a dedicated display somewhere along the wall of the court. However, with the advent of Hawk-Eye and a more widespread use of ball-tracking technologies, we’ve been able to collect much more in-depth data on strokes other than just the serve. I was therefore happy to see that one of the pieces of data made available to the public during the recently concluded Rolex Monte-Carlo Masters was the average spin rates and velocities of the groundstrokes hit during some of the matches.
Before we get to the data itself, a short disclaimer. First, the data was not available for every match played in the main draw; I’m assuming this is because some of the outside courts are not equipped with the necessary ball-tracking technology. Second, the average spin rates don’t differentiate between strokes hit with topspin and with backspin. This is not much of an issue on the forehand side, as the vast majority of forehands on the men’s tour are hit with topspin. The use of backspin is much more prevalent on the backhand side, but for every match there was just one raw spin number for all the backhands hit by a particular player. With that being said, here are some of the interesting trends from the 33 matches that had the data available (all data courtesy of ATP Tour).
Forehands are hit with more spin and velocity across the board
Below are the comprehensive spin rate and velocity statistics from all 33 matches:
|Forehand Spin (rpm)||Backhand Spin (rpm)||Forehand Velocity (km/h)||Backhand Velocity (km/h)|
There were 33 matches in the dataset, with 66 total “observations” (two per match: one for each player). In all 66 cases, the forehand spin rate was greater than the backhand spin rate. Furthermore, in 65 cases, the average forehand velocity was greater than the average backhand velocity; the lone exception being Hubert Hurkacz in his Round of 32 match, where his average forehand velocity was 111.5 km/h, while his average backhand velocity was 111.8 km/h.
Let’s combine this with the typical placement of the groundstrokes. Below are the placement breakdowns for Stefanos Tsitsipas and Andrey Rublev from their finals match; they are fairly representative of the overall trend. Forehands are the first gallery, backhands second.
On the forehand side, both Rublev and Tsitsipas preferred to aim their forehand into their opponent’s backhand, but the split is much closer to 50-50 than it is for the backhands. Forehands are hit faster, with more spin, and placed more unpredictably than backhands. This reinforces the traditional view of the forehand as the “sword,” and the backhand as the “shield;” the men’s groundstroke game is really a battle for forehands. At the same time, I think a backhand down the line is a tremendous weapon in today’s men’s game to counter this strategy, but that is for another blog post.
Correlations between spin rates and velocities
What I wanted to look at next is the relationship between the spin rates on strokes and the average velocities. Do groundstrokes hit at faster velocities spin at higher rpms? Are flat strokes faster than “spinnier” strokes? Here is the table of the correlation coefficients:
|Variable 1||Variable 2||Correlation Coefficient|
|Backhand Spin||Backhand Velocity||0.0561|
|Forehand Spin||Forehand Velocity||0.3024|
|Forehand Spin||Backhand Spin||0.6381|
|Forehand Velocity||Backhand Velocity||0.6370|
Starting from the top, the relationship between backhand spin and backhand velocity seems to be completely random; knowing a spin rate or a velocity tells you nothing about the other variable, at least for the matches in the current data set – I wonder if this might be due to the fact that we’re lumping topspin and backspin backhands together. There is a stronger positive relationship between the forehand spin and forehand velocity, even though it is still only a low to moderate relationship. The main takeaway from the first two lines in the table above is that fast groundstrokes can come in different shapes; corollary being that spinny groundstrokes come at different velocities. One example to illustrate this takeaway on the forehand side:
|Player||Round||Forehand Velocity (km/h)||Forehand Spin (rpm)|
The forehands of Tsitsipas and Davidovich Fokina in their round of 32 matches came in at about the same velocities, but the forehand of Tsitsipas was spinning about 500 rpm faster than Davidovich Fokina’s. Tsitsipas’ forehand will feel “heavier” to the opponent; we’ll return to this point towards the end of the article.
The second big takeaway from the correlation table is the much stronger positive correlation coefficients between the forehand and backhand spin rates, and the forehand and backhand velocities. In simple terms, when a player hits the ball hard from one side, he tends to hit it hard from the other side as well. Similarly, a player with a spinny forehand will most likely have a relatively spinny backhand as well.
This, to me, is especially interesting on the spin side. I would think that correlation would be weaker there; i.e. that players with spinny forehands might still have flat backhands. Forehands and backhands are hit with different grips; a grip on the racket plays a big part in the approach angle of the face of the racket as it makes contact with the ball; and finally the approach angle plays a large part on the spin imparted on the ball (spin and flight of the ball is physics; rocket science really. A rocket scientist I am not, this is overly simplified). What the data from Monte Carlo would seem to suggest is that players with more extreme forehand grips, for example, are more likely to have extreme backhand grips. Similarly, if a player has a grip closer to continental on the forehand (flatter), he’ll most likely have a flatter grip on the backhand as well. There’s a level of consistency in how he hits the ball from both sides.
Let’s finish up with the fun stuff: leaderboards! Who hit the fastest and spinniest forehands in Monte Carlo? Velocity comes first: below are the players with the forehand velocities in the 90th percentile and better.
|Player||Round||Forehand Velocity (km/h)|
And here are the players with forehand spin rates in the 90th percentile and better.
|Player||Round||Forehand Spin (rpm)|
What makes Nadal’s forehand untouchable is its combination of speed, spin, and the fact that it comes from the left side. The only other player appearing in both of the above tables is the eventual Monte Carlo champion Stefanos Tsitsipas. Forehands coming in at high speeds, and high spin rates, tend to bounce way up high, and opponents are often forced to make contact either back behind the baseline, or in uncomfortable positions around shoulder height. It is extremely challenging to return those forehands back with interest. Also, Casper Ruud is already ranked #24 ATP as of this writing; his way into the Top 20 and higher will be paved by his forehand. If he could add a few km/h to the stroke, he would be in the conversation for the heaviest forehand in the game after Nadal hangs up his rackets.
On to the backhands, velocity first. These are the players with backhand velocities in the 90th percentile and higher:
|Player||Round||Backhand Velocity (km/h)|
Rafael Nadal in his round of 16 match was absolutely bludgeoning the ball. Also, we can see a lot of the same names from the forehand velocity leaderboard in the table above: Nadal, Ramos-Vinolas, Davidovich Fokina, and Fabio Fognini all make an appearance in both velocity leaderboards. This is a good illustriation of the 0.6 correlation coefficient between the forehand and backhand velocities. If you like fast groundstrokes, these are your guys.
How about spinny backhands?
|Player||Round||Backhand Spin (rpm)|
Neither Tsitsipas nor Ruud are in the backhand velocity leaderboard, but both are featured in the forehand spin leaderboard, further illustrating the relationship between the spin of the groundstrokes, and a much weaker relationship between the spin and velocity of the individual strokes. Casper Ruud hits a two handed backhand, while Tsitsipas has a one hander.
Rafael Nadal was, unsurprisingly, the king of groundstroke velocity in Monte Carlo, ranking first in both the forehand and backhand velocity leaderboards. Casper Ruud was the unofficial king of topspin, placing first in both spin leaderboards. If the conditions in Paris are fast during the French Open – hot days, no rain, firm clay – watch out for Ruud making an appearance in the second week of the tournament.