In 2016, two things started happening in baseball: there were more home runs than ever before, and pitchers started getting more blisters. While MLB has no idea what specifically caused the homer surge, Dr. Meredith Wills of The Athletic thinks she’s found the cause for both: thicker lacing yarn on the outside of the baseball.

Shohei Ohtani is the latest victim of MLB’s continuing blister issues

Not even Shohei Ohtani, a gift to the game of baseball, is immune to this pesky pitcher injury. He left Wednesday night’s game between the Los Angeles Angels and the Kansas City Royals in the fourth inning with a blister on his right middle finger, something he’s had to do before. It’s not known if he’ll miss any time or go on the disabled list, but he’s just the latest to have this issue. Three other pitchers — Rich Hill, Matt Bowman, and Zac Rosscup — are currently on the disabled list with blisters that prevent them from pitching.

Shohei Ohtani has a blister on his pitching hand, and a change in baseball lacing yarn could be why. (AP Photo/Kyusung Gong) More

The problem goes back to 2016, which happened to be around the time home runs began surging in baseball. Guys like Hill, Marcus Stroman, and Aaron Sanchez started developing blisters, when they’d never before had those issues. In July 2017, a study from Ben Lindbergh at The Ringer found that pitchers had spent significantly more time out of commission with blisters in 2016 and 2017 than in previous nine years, and that individual blister injuries had also increased sharply.

Hill in particular has been hit hard. 2018 is the third year in a row he’s missed time due to blisters, and he’s even planning to ask MLB to allow pitchers to wear tape on their hands to cover blisters. That’s a lot better than some of his other remedies, which included urinating on his blistered hand. Ew.

Thicker lacing yarn could be causing it

When MLB released its report of the committee tasked with determining the cause of the home run surge, there was good news and bad news. The good news was that they determined what caused it: decreased drag on the baseball, which made it fly farther. But they had no idea what had decreased the drag on the baseball.

So Dr. Meredith Wills of The Athletic did an experiment. She took apart 26 balls — 12 from pre-surge 2014, and 14 from 2016-2017 — and tried to keep the materials as intact as possible. She measured a variety of factors between the materials of the two populations of balls, and found one major difference: the thickness of the bright red yarn used to stitch or lace the baseballs together. The yarn used in the 2016-2017 balls was 9 percent thicker than the yarn used in the 2014 balls.

Nine percent might seem small, but for pitchers who touch the ball with their bare hands more than any other kind of player, it could make a huge difference. Dr. Wills said that the thicker lacing yarn creates a “bumpier” seam. That could mean a baseball has different bumps and a textures than a pitcher is used to pitching with, leading to blisters for pitchers who grip the ball in a certain way.

The yarn could even be behind the home run surge

Dr. Wills also believes that the thicker laces could be a cause of the home run surge.

This introduction of thicker laces could very well be the factor that led to the home run surge. According to the executive summary released by MLB’s independent committee, “[M]anufacturing advances that result in a more spherically symmetric ball could have the unintended side effect of reducing the ball’s drag.” While it is unclear how much spherical symmetry would be gained from a 9.0% increase in lace thickness, it is unreasonable to assume that it would not make some contribution to drag reduction, thereby allowing the ball to carry farther.

There’s only one problem: Rawlings, the company that makes the baseballs, told Nathan that the stitching material wasn’t changed. However, if their yarn supplier made a change and didn’t tell Rawlings, then they wouldn’t even know there was a difference. Until the ball started flying and pitchers started getting a lot more blisters, that is.