Wills: How one tiny change to the baseball may have led to both the home run surge and the rise in pitcher blisters

From SABR member Meredith Wills at The Athletic on June 6, 2018:

Major League Baseball recently released its official report investigating the source of last season’s home run surge.  The independent committee concluded that the cause was the ball itself—specifically, a decrease in the ball’s drag coefficient. However, they were unable find the reason for this change.

After taking apart and examining twenty-six baseballs, not only have I found a possible explanation for the decrease in drag, but one that could also account for the recent spike in pitcher blister injuries.

Working under the hypothesis that pre-2015 balls are structurally different than 2016-2017 balls in some way, I systematically disassembled two populations of baseballs—twelve from 2014 and fourteen from 2016-2017. A Major League baseball is made up of a core (the “pill”) surrounded by five layers: an inner layer of thick grey yarn; a middle layer of white yarn; an outer layer of thin grey yarn; a thin layer of cotton thread; and a leather cover. The cotton thread is held in place by glue, while the two pieces of the leather cover are stitched together by red laces.

To gather my data, I removed the leather covers by unstitching the laces, rather than cutting them. I then cut away the cotton thread layer (as the glue made unwinding the thread untenable), carefully unwound and separated the three yarn layers, and removed the pill. The photo below shows the disassembled materials in comparison with an untouched baseball.

Read the full article (subscription required): https://theathletic.com/381544/2018/06/06/how-one-tiny-change-to-the-baseball-may-have-led-to-both-the-home-run-surge-and-the-rise-in-pitcher-blisters/

Originally published: June 6, 2018. Last Updated: June 6, 2018.