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MLB’s Blister Problem Is Real

Data confirm that more major league pitchers are suffering blister injuries than at any point in recent history. How widespread is the issue — and is the baseball to blame?

(Getty Images/Ringer illustration)
(Getty Images/Ringer illustration)

Less than two weeks after Opening Day, my Ringer MLB Show cohost Michael Baumann and I bypassed a wealth of potential podcast topics to do a segment about blisters. Dodgers starter Rich Hill, who’d signed a three-year, $48 million deal to stay in Los Angeles in December, had suffered a recurrence of his stubborn blister problems from 2016, leaving his value to the team in doubt. His chronic case of blisters seemed so serious that speaking to just one dermatologist on the podcast wouldn’t do, so Michael and I talked to two dermatologists about treatments Hill could try. Days later, Hill would tell Alanna Rizzo of SportsNetLA that he was hoping for a "medical miracle" to spare him from further finger problems, which his training staff’s therapy and his manager’s quick hooks hadn’t helped prevent.

Michael and I figured that our big blister show would have a short shelf life. Almost three months later, though, blisters have become a bigger story in baseball than they were then. Hill, who’s back in action and, for the time being, blister free, is one of many high-profile pitchers who’ve battled the problem this year, including Corey Kluber, Noah Syndergaard, Jake Arrieta, Johnny Cueto, and David Price. The latest starter to join the blister brigade is Toronto’s Marcus Stroman, who last week was pulled from a start against the Yankees after 79 pitches because of a developing blister. Although Stroman doesn’t appear likely to miss extended time (he threw 109 pitches in his next start against the Astros), he isn’t taking the condition quietly. After that game against New York — thinking, perhaps, of his teammate Aaron Sanchez, who’s been sidelined by blisters for parts of both this season and last — he complained about a blister "epidemic" in baseball.

"For MLB to turn their back to it, I think that’s kind of crazy," Stroman said. "I have no theory. But obviously, I mean, it’s not a coincidence that it’s happening to so many guys all of a sudden. It’s not a coincidence."

Stroman, who said that he’d never had blister problems before, wouldn’t elaborate on why he believes that the blister cases are connected. But his reference to MLB’s back-turning seemed like an allusion to the memo that the league had distributed days earlier, in which it sought somewhat unconvincingly to refute the idea that the construction of the baseball itself has changed in recent years, as has been reported by The Ringer and FiveThirtyEight (and echoed by many players, coaches, and managers). Stroman seemed to be suggesting that the baseball is responsible not just for the game’s record home run rates, but for its alleged blister epidemic too.

Aaron Sanchez (Getty Images)
Aaron Sanchez (Getty Images)

Other pitchers, including Hill, have made their speculation about the baseball and blisters more explicit. "Now that we’re starting to see this thing occur with more pitchers around the league, and it’s not just me, if you look at it that way, the ball could be the issue," Sanchez said on Friday. Hill, who like Stroman has noted that he never had blisters before 2016, also also openly wondered about the ball, saying, "There’s got to be something, right? There’s more evidence this year than there ever has been of blisters in pitchers."

Thus far, the only evidence about increased blister rates that’s appeared in response to Stroman’s comments has been anecdotal. Today, I come bearing blister data. And while the word "epidemic" might overstate the severity of the situation, the numbers back up the idea that blisters have become much more common in the majors since the start of last year.

The most comprehensive public database of baseball injuries belongs to Corey Dawkins, an athletic trainer and injury-prevention specialist at the Micheli Center for Sports Injury Prevention who also started Baseball Injury Consultants. Dawkins sent me his records for blisters, fingernail tears, and finger lacerations suffered by major league pitchers in the past decade. I went through the non-blister entries and removed any for which I failed to find a tie to blisters, including lacerations that stemmed from drone repairs, broken beer mugs, reckless celebration, dish-doing, and even standing up from the dugout bench. Although fingernail tears can be related to the baseball’s physical properties — in 2007, Tigers reliever Joel Zumaya described throwing a breaking ball that "caught on the seams and pulled [his] nail back" — I focused only on blisters to test the contentions of Stroman, Sanchez, and Hill. I also supplemented Dawkins’s data with additional info from Pro Sports Transactions.

The first graph below displays days missed by MLB pitchers — including DL stints and day-to-day ailments — because of blister-related injuries over the past 10-plus seasons. The second graph shows the number of MLB pitchers who’ve had blister-related database entries in each season, both with and without repeat appearances. The 2017 counts are for the season to date, not projected full-season totals.

While the data may seem damning, let’s include a few caveats. Clearly, this isn’t a complete record of MLB blisters, in that it doesn’t include any that weren’t publicly reported. (In an article I linked to above, Hill told Bill Shaikin of the Los Angeles Times that other Dodgers pitchers who’ve had blisters this year have treated them "without public disclosure of the condition.") It’s also possible that pitchers have been more open about blisters lately because of the growing scrutiny surrounding the ball, or that some teams have used blisters as a justification for giving their pitchers extra rest, which could skew the stats. Lastly, Sanchez and Hill have combined for more than a third of the blister entries, and almost 40 percent of the days missed because of blisters, from 2016 to 2017, another factor that might make the blister scourge seem more widespread than it actually is. Still, based on the best data we have, MLB’s blister increase is real.

"No question that there is an increase from previous years," former Dodgers head athletic trainer and VP of medical services Stan Conte, who now runs an injury-management consulting company, tells me via email. "The million dollar question is why. I think with all the talk about the perceived changes in the ball, that has to be on the top of the list. We are also looking into see[ing] if there is an increase in the minor leagues as well. This is more difficult data to get."

It’s possible that the blister spike has nothing to do with the ball: It could be a fluke or a product of other developments, such as altered grips or the trends toward higher velocities and fewer fastballs. (Among starters with at least 100 innings pitched from 2016 to 2017, only Lance McCullers, who also missed time with a blister last year, has thrown a curveball more frequently than Hill.) If the ball is the culprit, though, the most likely mechanism of injury would be a change in seam height. Both The Ringer’s direct baseball testing and FiveThirtyEight’s statistical inquiries — as well as the seam-height data in the ball-testing-results summary that MLB provided to The Ringer — indicate that the seams on the ball are lower now than they were before 2016. "The seams are different and the balls are a lot harder,’’ Mets manager Terry Collins recently told USA Today. "And with these seams different, you’re seeing guys getting more blisters."

The catch is that I’ve encountered conflicting opinions about whether the seams are higher or lower, and whether one change or the other would be more likely to lead to blisters. Hill and Justin Verlander agree that the seams are lower, with Verlander alleging that "there’s not much of a seam on the ball anymore." But Hill’s teammate Brandon McCarthy, who’s also struggled with blisters this season, tells me via Twitter direct message that the seams "100% feel bigger" to him. "All I know is the seams feel huge to me now — almost like college balls — and I get a blister every single start now, which has never happened," McCarthy says. (His most recent entry in the blister database before this year’s issue dates from 2007.)

Similarly, the trainer and doctor I spoke to for this story disagree about which seam extreme would pose the greater blister risk. "My feeling about the seams [is] that the lower they are, it would be more inclined to cause them," Dawkins says via email. "The surface friction also plays a large role, regardless of seam height. The slightest variation in coefficient of friction between the seams, the leather, and the skin could have dramatic effects on blister outcome." Yet Dr. Charles Crutchfield, who serves as team dermatologist for the Twins and other Minnesota professional sports teams, says, "Blisters are a result of friction. The higher the stitch, the greater the friction, the greater the chance for a blister."

Both explanations sound plausible. As former major league pitcher (and current Diamondbacks pitching strategist) Dan Haren puts it via direct message, "Higher seams would cause more blisters, but I suppose if the seams were lower, guys would have to try harder to generate spin." Maybe that extra effort could cause blisters too.

For now, it seems that we can come to two tenuously related conclusions: Blisters have become more common among major league pitchers, and the baseball’s seams have changed. Based on public reports, the number of MLB pitchers afflicted by blisters remains fairly small, except when compared to the totals from previous years. One’s perception of whether the trend toward blisters constitutes an epidemic may depend on whether one is, plays with, or roots for one of those pitchers — or, perhaps, whether one owns any of them on a fantasy team. But for anyone who wanted more evidence that the baseball is different, blisters have obliged.