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Everyone’s Just Guessing About Matt Harvey’s Innings Limit

Mets pitcher Matt Harvey was caught in a tabloid cacophony last week after his agent, Scott Boras, spoke candidly about how many innings Harvey should pitch this season. Harvey, who came back from Tommy John surgery at the beginning of the year, was said to be on a soft limit of about 180 innings,1 as recommended by his surgeon. The Mets want Harvey to pitch in the postseason, Boras wants Harvey to sit out if it means exceeding 180 innings, and Harvey … Harvey seems to want both things.

Boras’s approach seems reasonable: Limiting the innings of a young pitcher who may still be recovering from a serious injury seems like it might be wise. The trouble is that we have no idea whether innings limits work.

There’s no question that pitching puts great stress on the arm. Accordingly, some studies of adolescent pitchers have found a link between an athlete’s innings pitched and the probability of future injury. The logic is clear: The more pitches thrown, the more wear and tear on the arm. Based on that, a hard limit on Harvey’s workload appears to be a good idea.

But there’s no guarantee that what goes for amateurs also goes for pros. Harvey and all other MLB pitchers are a particularly talented and hardy group of throwers relative to those who play in high school, the minors or even college. It’s plausible that each additional pitch does less damage to them than it would to your local high school pitcher. Supporting this idea, a recent paper analyzing MLB pitchers 25 and younger (Harvey is 26) found no clear link between the number of innings pitched and future injury rates.

It’s possible that Harvey represents a special case because of not only his youth, but also his previous bout of elbow trouble. Boras made this argument by presenting a set of four pitchers comparable to Harvey, each of whom came off Tommy John surgery and pitched more than 200 innings in the next year. All four suffered complications.

But a sample of four pitchers can hardly provide conclusive evidence, and the Mets’ own preseason study (using comparable players) produced the opposite conclusion. That two studies using similar methods could produce conflicting verdicts underscores the difficulty of predicting pitcher health. As Mets general manager Sandy Alderson put it, “It’s not science.”

One of the major problems is that any simple calculation of workload (like IP) is a flawed measure of fatigue and thus injury risk. Not all pitches inflict the same damage upon the arm, and poor mechanics cause injury much more quickly. The future of injury analytics will likely depend on better ways of gauging pitcher health that measure not only the workload but also the technique of the pitcher and how it changes over time. Newer technologies such as motion tracking systems and wearable sensors offer the promise of novel metrics that could be predictive, but most such systems are in preliminary stages of development or are just being deployed. Until those new technologies develop further, the Mets, Boras and Harvey are flying blind.

Footnotes

  1. He’s currently at 166 1/3 innings, giving him about two more starts before he hits the limit.

Rob Arthur is FiveThirtyEight’s baseball columnist and also writes about crime.

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