I’ve been going on all year about the ball all year, about how it wasn’t flying as well as it did in previous years. At the Japan Series, former pitcher Hiromi Makihara was surprised to find that someone outside the loop would know that there was a problem. I told him it was simple arithmetic, when home runs drop by 35 Percent, it’s no secret. He was rightly impressed.
Having heard from a member of one club’s analytics staff that the yarn used to stitch the covers on the balls was fraying on hard contact, I assumed the issue was yarn from a new supplier that was not up to spec. But Makihara revealed at the Japan Series that the problem was related to a change in the manufacturing process after Mizuno moved its production of NPB balls in the summer of 2023 from China to Taiwan, which a senior NPB official confirmed.
As the season went on, it became clear that from some time in June the balls became a little more lively. I assumed the problem with the manufacturing process had been solved by switching the yarn, but the world’s leading expert on baseballs, Dr. Meredith Wills, set me straight when I ran into her at the winter meetings in Dallas a week ago.
Wills, as some of you might remember, is the astrophysicist who unraveled the mystery of the lively, finger-blister inducing MLB 2018 baseballs: “When stars align: How an astrophysicist unraveled a baseball mystery .”
When I mentioned my speculation about this year’s balls in Japan and told her the drop off in home runs was over 30 percent, she said, “THAT’s the ball.”
HRs as percentage of fly balls, and 2024 drop off
| Years | April | May | June | July | Aug. | Sept. |
|---|---|---|---|---|---|---|
| 2022, 2023 | 5.9% | 6.6% | 6.4% | 6.8% | 6.6% | 6.6% |
| 2024 | 4.0% | 4.4% | 4.7% | 5.2% | 5.9% | 5.4% |
| Diff | -32% | -34% | -27% | -25% | -10% | -18% |
She suggested there were two likely solutions provided NPB figured out the problem in March: Either the production was switched back to China, or some changes were made to the process in Taiwan, provided that factory had already been making baseballs before the switch.
Dr. Wills explained how when MLB began using the same specs for the balls in Triple-A, those minor league balls used yarn of the same thickness, but was not as strong because the cheaper yarn was made with shorter fiber strands, and the minors ran out of balls earlier than predicted.
She said she believed that whatever fix Mizuno had employed had been to change the manufacturing process because similar issues had occurred when MLB switched its production to a new country and the people suddenly tasked with stitching the balls together lacked the skill needed to maintain the old quality.
