The new Statcast Sprint Speed metric is now available to the public and the leaderboard is both fun to look at and about as revelatory as many trade rumour tweets. At the top is Billy Hamilton, who is fast. At the bottom is Albert Pujols, who is not. The metric is simply the player’s speed in feet per second in their fastest one-second window, ranging from around 30 feet/second in Hamilton’s case to 23 for Pujols.

While it is intruiging to see that Hamilton beats out the likes of Byron Buxton, or that Marlins catcher J.T. Realmuto is ludicrously fast compared to his peers (1.3 f/s faster than the next-best catcher), this new source of data starts to offer some really fascinating possibilities when utilised in relation to other statistics, and just how much a player’s raw speed influences the quality of their contributions in-game. In this case specifically, comparing sprint speed with FanGraphs’ catch-all Base Running stat, or BsR.

The in-depth explanation of BsR is best left to FanGraphs’ glossary page on the topic, but a brief overview is that it combines weighted statistics for stolen bases (wSB), double plays (wGDP), and all other situations in which runners could potentially advance a base (Ultimate Base Running, or UBR) into a total number of runs above or below average. This then forms the baserunning component of FG’s WAR calculation.

In order to discern the relationship between these two statistics, the sprint speed per second above average was calculated for each of the 375 players who appear on the leaderboard (with 27 ft/s being average) and then plotted against each player’s BsR for the 2017 season, the results of which can be seen below.

That’s a real relationship, but also not a particularly strong one. The R squared for this dataset is 0.244; in other words, around a quarter of BsR is explained by sprint speed alone, so there’s plenty more going on here. Much like the leaderboard itself, that probably isn’t too much of a surprise. Fast runners are not always valuable baserunners, and as explored here last month, even Hamilton didn’t succeed as often as might have been expected early in his career.

Of course, it will come as no surprise to anyone to learn that Hamilton is in the very top right of the plot. He’s on track for a third straight season of double-digit runs produced on the bases. The prime example of a speedster who really hasn’t been fully utilising their tools to full effect is Rays outfielder Mallex Smith, who is the slightly below-average BsR datapoint at 2.4 f/s above average. Part of the problem here is that Smith has just 157 PA this season (and at this stage it should be noted that just over a half-season isn’t ideal for BsR in any case, but even more so for call-ups like Smith). But he’s also been -1.6 runs below average by UBR and not much over average in the other two components. That will have something to do with the fact that he’s twice been out at third and also been caught stealing home, barely. No matter how fast you are, a poor decision by the baserunner and a good one by a fielder will get you out, as Smith and Manny Machado illustrate below.

The oddly positive BsR point at almost -3 f/s below average is Brewers catcher Jett Bandy. The 27-year-old is definitely not fast, with a 24.2 f/s sprint speed, but like Smith, he hasn’t played a ton, and unlike Smith, he hasn’t made any mistakes on the basepaths, at least not mistakes that have been punished. He is yet to be thrown out on the bases, partly because he rarely tries to take the extra base (XBT%), doing so just 18% of the time per Baseball-Reference (the league average is 40%). This will get worse; Bandy was at -3.5 BsR last year, and over a longer stretch of time, never taking the extra base is going to hurt in UBR because he’ll start to perform below the average run expectancy for those situations. Nonetheless, Bandy, and to a lesser extent Pujols, Brian McCann and Miguel Montero, who are the three left-most datapoints, demonstrate the value of knowing your limitations on the bases, something Smith is probably still figuring out.

Two more players worth highlighting are on the same team, are the second and third best baserunners by BsR in the majors, yet only rate as 1 f/s above average in sprint speed: Mookie Betts and Xander Bogaerts. The Red Sox duo are both very efficient basestealers, at 85% and 90% success respectively, but Betts has double the attempts of his teammate, providing a higher wSB value despite his slightly lower success rate. Bogaerts is rated slightly higher by UBR, with Betts out at home twice and Bogaerts also scoring from second on a single 11 of 12 times, as opposed to 15 of 19 for Betts.

Where Betts really excels is taking the extra base, however: he leads all qualified players with an incredible 72% XBT%, making Bogaerts’ perfectly good 61% look rather ordinary. In short, it’s not essential to be close to the league’s fastest player to be among the most valuable, and perhaps this also speaks to the importance of how players take the turns round the bases and how well they maintain their speed, which Betts is clearly very good at. Hopefully this also makes Red Sox fans feel a bit better about their team’s incredible ability to make outs on the bases, which they have done a league-leading 50 times this year.

A final player of note, languishing at the lowest point of the chart, is Mets ‘shortstop’ Asdrubal Cabrera, who does not appear to be particularly slow by sprint speed — only 1.1 f/s below average — yet has cost the Mets 7.3 runs by BsR’s estimation. Cabrera has not only grounded into a ton of double plays, doing so in 20% of situations when the league average is 11%, he has barely taken the extra base more often than Bandy, at 24%, a mark actually slightly lower than Pujols at 27%. In just three of 21 cases has he advanced from first to third on a single. Cabrera has played through multiple leg injuries in recent years and has declined one foot per second from essentially average in sprint speed in 2015 (the first year of Statcast data), when he was also average by BsR. Even for Cabrera, not everything has gone away: he’s still three-for-four in stolen base attempts this season. Sprint speed tells us a decent amount about baserunning prowess, but there’s a whole lot more to running the bases than speed.



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