For the last couple of years, some tennis broadcasts have featured “distance run” stats, tracking how far each player travels over the course of a point or a match. It’s a natural byproduct of all the cameras pointed at tennis courts. Especially in long rallies, it’s something that fans have wondered about for years.

As is often the case with new metrics, no one seems to be asking whether these new stats mean anything. Thanks to IBM (you never thought I’d write *that*, did you?), we have more than merely anecdotal data to play with, and we can start to answer that question.

At Roland Garros and Wimbledon this year, distance run during each point was tracked for players on several main courts. From those two Slams, we have point-by-point distance numbers for 103 of the 254 men’s singles matches. A substantial group of women’s matches is available as well, and I’ll look at those in a future post.

Let’s start by getting a feel for the range of these numbers. Of the available non-retirement matches, the shortest distance run was in Rafael Nadal’s first-round match in Paris against Sam Groth. Nadal ran 960 meters against Groth’s 923–the only match in the dataset with a total distance run under two kilometers.

At the other extreme, Novak Djokovic ran 4.3 km in his fourth-round Roland Garros match against Roberto Bautista Agut, who himself tallied a whopping 4.6 km. Novak’s French Open final against Andy Murray is also near the top of the list. The two players totaled 6.7 km, with Djokovic’s 3.4 km edging out Murray’s 3.3 km. Murray is a familiar face in these marathon matches, figuring in four of the top ten. (Thanks to his recent success, he’s also wildly overepresented in our sample, appearing 14 times.)

Between these extremes, the *average* match features a combined 4.4 km of running, or just over 20 meters per point. If we limit our view to points of five shots or longer (a very approximate way of separating rallies from points in which the serve largely determines the outcome), the average distance per point is 42 meters.

Naturally, on the Paris clay, points are longer and players do more running. In the average Roland Garros match, the competitors combined for 4.8 km per match, compared to 4.1 km at Wimbledon. (The dataset consists of about twice as many Wimbledon matches, so the overall numbers are skewed in that direction.) Measured by the point, that’s 47 meters per point on clay and 37 meters per point on grass.

**Not a key to the match**

All that running may be necessary, but covering more distance than your opponent doesn’t seem to have anything to do with winning the match. Of the 104 matches, almost exactly half (53) were won by the player who ran farther.

It’s possible that running more or less is a benefit for certain players. Surprisingly, Murray ran less than his opponent in 10 of his 14 matches, including his French Open contests against Ivo Karlovic and John Isner. (Big servers, immobile as they tend to be, may induce even less running in their opponents, since so many of their shots are all-or-nothing. On the other hand, Murray outran another big server, Nick Kyrgios, at Wimbledon.)

We think of physical players like Murray and Djokovic as the ones covering the entire court, and by doing so, they simultaneously force their opponents to do the same–or more. In Novak’s ten Roland Garros and Wimbledon matches, he ran farther than his opponent only twice–in the Paris final against Murray, and in the second round of Wimbledon against Adrian Mannarino. In general, running fewer meters doesn’t appear to be a leading indicator of victory, but for certain players in the Murray-Djokovic mold, it may be.

In the same vein, *combined *distance run may turn out to be a worthwhile metric. For men who earn their money in long, physical rallies, total distance run could serve as a proxy for their success in forcing a certain kind of match.

It’s also possible that aggregate numbers will never be more than curiosities. In the average match, there was only a 125 meter difference between the distances covered by the two players. In percentage terms, that means one player outran the other by only 5.5%. And as we’ll see in a moment, a difference of that magnitude could happen simply because one player racked up more points on serve.

**Point-level characteristics**

In the majority of points, the returner does a lot more running than the server does. The server usually forces his opponent to start running first, and in today’s men’s game, the server rarely needs to scramble too much to hit his next shot.

On average, the returner must run just over 10% further. When the first serve is put in play, that difference jumps to 12%. On second-serve points, it drops to 7%.

By extension, we would expect that the player who runs further would, more often than not, lose the point. That’s not because running more is necessarily bad, but because of the inherent server’s advantage, which has the side effect of showing up in the distance run stats as well. That hypothesis turns out to be correct: The player who runs farther in a single point loses the point 56% of the time.

When we narrow our view to only those points with five shots or more, we see that running more is still associated with losing. In these longer rallies, the player who covered more distance loses 58% of the points.

Some of the “extra” running in shorter points can be attributed to returning serve–and thus, we can assume that players are losing points because of the disadvantage of returning, not necessarily because they ran so much. But even in very long rallies of 10 shots or more, the player who runs farther is more likely to lose the point. Even at the level of a single point, my suggestion above, that physical players succeed by forcing opponents to work even harder than they do, seems valid.

With barely 100 matches of data–and a somewhat biased sample, no less–there are only so many conclusions we can draw about distance run stats. Two Grand Slams worth of show court matches is just enough to give us a general context for understanding these numbers and to hint at some interesting findings about the best players. Let’s hope that IBM continues to collect these stats, and that the ATP and WTA follow suit.