Arthur: Can we figure out which teams are the best at preventing injuries?

From SABR member Robert Arthur at Baseball Prospectus on September 19, 2014:

At the team level, injuries are as mysterious as they can be crippling. The Texas Rangers are suffering a whirlwind of pitcher injuries that threatens to break records and has certainly been one of the primary causes of their disappointing season. Meanwhile, teams full of aged veterans like the Yankees and Phillies have somehow managed to evade their fair share, albeit without benefiting very much.

Differences like these suggest asking whether some teams are better at limiting injuries than others. Ben Lindbergh (with the help of Russell Carleton) tried to tackle this issue a few days ago in the context of the Pirates’ remarkable run of injury prevention. They found little detectable signal of any team having an ability to reduce injuries.

However, their study was not without caveats. For one thing, they did not control for the players on each team, and we know that certain players are more likely to suffer injuries than others. Because players turn over from year to year, it stands to reason that failing to control for their unique injury probabilities could confound an analysis of the team’s injury-prevention abilities. (This caveat was noted in the article.)

I decided to undertake a deeper analysis of injury at the team level by controlling for the players involved. I showed in a previous article that the major determinants of days missed are 1) the number of days the player missed in each of the three years prior, and 2) age. The former encompasses the effect of a player’s injury history, the latter the natural buildup of risk due to senescence. With this said, the majority of the predictive power of the model stems from the days missed in the two prior years. Because all four variables (age and injury history in the last three years) are correlated with each other, most of the information about a player’s injury proneness can be captured in the days he has missed in only the last two years.

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Originally published: September 19, 2014. Last Updated: September 19, 2014.