Arthur: Using PITCHf/x to predict hitter injuries

From SABR member Robert Arthur at Baseball Prospectus on February 6, 2015:

Injuries, I think we can all agree, are a deplorable scourge on baseball. They remove our favorite players indiscriminately from the field, or ruin their effectiveness. They can take teams that are great on paper and reduce them to smoldering piles of ash (see the Texas Rangers, 2014). Even though injuries appear random, the result of bad luck and stochastic variation, they are (to a limited extent) predictable. Based on prior research, it turns out that commonsense factors can predispose position players to injury.

In particular, my last foray into the subject found that age as well as the number of days missed in the past three seasons could provide a reliable prediction into how many days each position player would miss in the coming year. However, the accuracy of these predictions was modest, and required extensive information from prior years. It would be desirable to make further improvements upon these injury predictions, but in the absence of other possible sources of information, prospects seemed slim.

This is where PITCHf/x data may be of some use. There is precedent for employing this kind of data, albeit on the mound: Josh Kalk and Noah Woodward developed injury prediction tools for pitchers utilizing information like velocity and movement. When pitchers began to exhibit abnormal patterns, Kalk and Woodward could sometimes diagnose injuries. Of course, hitters present a different set of challenges, because PITCHf/x doesn’t directly measure their performance. Instead, as I’ve written before, we have to read out hitter ability in terms of the way pitchers approach them. When it changes, we can use that information to diagnose a lurking problem.

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Originally published: February 6, 2015. Last Updated: February 6, 2015.