The Effect of the 2021 MLB Foreign Substance Policy on Pitcher Injury Rates and Statistics.

Background: Major League Baseball (MLB) implemented a new foreign substance policy in June 2021. The effect of the new policy on pitcher injuries, wild pitches, hit batters, and pitching statistics is unknown.

Purpose: To determine the effect of the new foreign substance policy regarding grip enhancement before and after its implementation on pitcher injury rate, wild pitches, hit batters, base on balls, strikeouts (SO), and home runs (HR).

Study design: Descriptive epidemiology study.

Methods: MLB pitchers from the 2019 season were retrospectively compared with the pitchers from the 2022 season. Data were retrospectively collected on injuries and pitching statistics utilizing publicly available data. Primary outcome measures included pitcher injury rate, wild pitches, and hit batters. Secondary outcome measures included base on balls, SO, and HR. A nonparametric Wilcoxon rank-sum test was utilized for computing P values when comparing unadjusted non-normally distributed continuous outcomes and covariates between 2019 and 2022, which was adjusted for number of batters faced using either a linear regression model for adjusting means or a quantile regression model for adjusting medians.

Results: In total, 828 pitchers in the 2019 season and 867 pitchers in the 2022 season were evaluated and included in this analysis. Pitcher overall injury rate per 1000 batters faced, hit batters, and SO did not show a statistical difference (P > .05). There was a statistically significant decrease in the adjusted number of wild pitches (2.9 vs 2.51; P = .04), adjusted earned run average (ERA) (4.51 vs 3.75; P < .01), adjusted base on balls (22.6 vs 21.1; P = .04), and adjusted HR (8.1 vs 6.1; P < .01) between the 2019 and 2022 seasons (P < .05).

Conclusion: Our study showed that the effect of MLB policy enforcement regarding grip enhancement did not demonstrate a change in pitcher injury rate, hit batters, or SO; however, there was a significant decrease in wild pitches, ERA, and base on balls. As a result, the new policy appears to maintain previous injury rate and pitching statistics while attempting to control for foreign substance use.