Major League Baseball's experimental Automated Ball-Strike (ABS) system, which allows teams to challenge ball and strike calls, has highlighted a pattern: veteran umpires are having a disproportionately high number of their calls overturned. The system, which began this season, offers teams two challenges per game, with the challenge kept if successful.
Several veteran umpires, including CB Bucknor, Andy Fletcher, and Chris Segal, have shown overturn rates exceeding 75%. For instance, Chris Segal has an 85.7% overturn rate, and CB Bucknor, despite fewer challenged calls, also has a high overturn rate. This indicates that their judgment on ball and strike calls frequently differs from the automated system's assessment, leading to a higher rate of successful challenges against their decisions.
Overall, the ABS system has seen 1,050 challenges this season, with a 54% success rate across the league as of a recent count. Approximately one out of every 74 pitches is challenged, translating to about 2.6% of all ball/strike calls, or one in every 39. The league averages 4.05 challenges per game, underscoring the frequent use of the system. While acknowledging that the total number of challenges is a small fraction of overall pitches called, experts note that an overturn rate north of 75% for individual umpires is significant and points to inconsistencies in their strike zone interpretation compared to the automated system.
