What Does Speed Do

One of the great things about the new metrics introduced via Statcast is they’re revealing aspects of the game that have long been hidden. While complicated metrics like barreled batted balls and catch probability are interesting and useful, I think the most exciting metrics are those that measure the visceral actions on the field. There’s something satisfying in knowing how hard a ball was hit or how fast a runner ran. Maybe it calls us back to the schoolyard, where nine-year-olds would challenge each other to all sorts of physical contests.

Yesterday, MLB released another Statcast leaderboard, this time measuring Sprint Speed. Speed has always been something that’s been tied to a player’s reputation. We might have a scout’s stopwatch reading, but for the most part, we know speed when we see it. Jarrod Dyson is fast. Nelson Cruz is not. But now we can precisely measure the speed of a player and compare it to his peers.

Briefly, Sprint Speed measures speed in terms of “feet per second in a player’s fastest one-second window.” These windows are measured using max-effort plays to remove the noise of players jogging around the bases or in the field. In his article introducing the metric, Mike Petrillo shows us that Sprint Speed has a high year-to-year correlation and a low threshold to establish a meaningful sample. League average Sprint Speed sit at a convenient 27.0 ft/s.

So what does sprint speed look like for the Mariners?

This plot, sourced from Baseball Savant, shows each position group with Mariners players highlighted. Jarrod Dyson is that pink dot way out to the right. Nelson Cruz is the yellow dot off to the left. There aren’t many surprises here. Everyone shows up where you’d expect them to, except for Taylor Motter. For someone who has nine stolen bases without being caught a single time, Motter’s Sprint Speed is surprisingly low (26.6 ft/s). That’s on par with Kyle Seager and players like Jay Bruce and Hanley Ramirez.

What about year-over-year changes in Sprint Speed? One of the emphases this offseason was to get faster and more athletic. The average Sprint Speed on the Mariners in 2016 was 26.7 ft/s. This year, it’s 27.1 ft/s. It may not seem like much, but a half a foot per second difference is pretty significant. What about individual differences. Below is a table showing 2016 and 2016 Sprint Speeds along with Base Running (BsR) scores from FanGraphs.

For the most part, most of the Mariners have maintained their speed from last year. Some of the notable changes include Jarrod Dyson and Jean Segura. Dyson has lost almost a half a foot per second, probably due to age, and Segura has dealt with two lower body injuries this season, sapping some of his speed.

BsR is the base running component of fWAR and combines stolen base success and non-stolen base plays. It’s calculated using run values and is a counting stat (zero is league average, ten runs is roughly equal to one win). As Craig Edwards showed in his article on FanGraphs, Sprint Speed has a decent relationship with BsR. There are always outliers though, like Danny Valencia. His Sprint Speed is a little above league average but he’s been one of the worst base runners in the majors this year. He’s just one for three on stolen base attempts but he’s also grounded into nine double plays and has made a number of outs on the basepaths.

Both Valencia and Motter illustrate some of the limitations of Sprint Speed. Based on his stolen base record, it’s likely Motter has great instincts for when to steal and can read a pitcher’s movement well. Valencia may be faster than average, but his Base Running score indicates he’s been a little too aggressive on the base paths (some of this may be the fault of his base coaches too). Simply running fast (or slow) can only get you so far. There is so much more that goes into running the bases well.

On the other hand, these data points confirm that the Mariners have one of the speediest outfields in baseball. We know Dyson is one of the fastest center fielders (Leonys Martin’s Sprint Speed was 28.0 ft/s last year, by the way), but now we know that Ben Gamel is the second fastest right fielder in baseball. That’s certainly one way to build the best outfield defense in the league.