Just in time for all of the air to have leaked out of Deflategate, we again have to talk about the balls.
Now it’s in Major League Baseball, which is experiencing a mammoth, multi-year spike in home runs without explanation. Unless, as a new study suggests, the baseball itself is “juiced,” having undergone subtle yet statistically significant changes in size and composition in recent years that make it come off the bat faster and travel farther.
An article published Wednesday by The Ringer related the results of an independent ball-testing experiment commissioned by sabermetrics guru Mitchel Lichtman. He bought authentic game-used baseballs on eBay from the periods prior to and following the 2015 All-Star break — viewed as a point of demarcation when the percentage of batted balls going for homers deviated upward — and sent them to the Sports Science Lab at Washington State University for rigorous high-impact testing.
The experiment found the batch of balls from 2016, as compared with those from the first half of 2015 (balls from the second half of 2015 were thrown out for being of unknown chronological origin), had a higher “coefficient of restitution” (COR) — read: were bouncier — as well as having lower seams and a smaller circumference. The cumulative effect of these factors is the new balls are estimated to travel an average of 7 feet more, which is the physics equivalent of an extra 1.4 mph of exit speed off the bat.
Lichtman calculated the COR increase in his post-spike sample was 2.6 standard deviations from the mean, the report says, or “unlikely to have happened by chance.” Translation: Something is different about the latest balls.
A couple of caveats are required here. One, the specs of all of the balls tested by Lichtman remain in MLB’s (relatively expansive) allowable ranges, which was a major point in the league’s general denial of the “juiced” ball theory.
“As a quality control effort, we routinely conduct in-season and off-season testing of baseballs in conjunction with our consultants at UMass-Lowell to ensure that they meet our specifications. All recent test results have been within the specifications,” MLB said Wednesday in a statement. “In addition, we used a third-party consultant to test whether the baseball had any impact on offense in recent years, and he found no evidence of that.”
The second caveat is that any alchemical change to the baseball would operate in concert with a number of variables to produce the ongoing home-run trend. For instance, noticing marginally longer flights on fly balls, hitters might add more uppercut to their swings (a higher launch angle) or change their risk-reward thinking (which also would yield more strikeouts) to get more balls in the air.