Overview
- Opening Night in San Francisco on Wednesday produced the first-ever challenge when Yankees shortstop José Caballero contested a called strike that was upheld, and on Thursday at Citi Field Mets catcher Francisco Álvarez recorded the first successful challenge to turn a ball into strike three.
- Only the batter, pitcher, or catcher can challenge by tapping their helmet within about two seconds, each team starts with two challenges, successful ones are kept, and a team that runs out gets one new challenge per extra inning.
- ABS uses 12 Sony Hawk‑Eye cameras and a private T‑Mobile 5G link to plot each pitch against a personalized, two-dimensional strike zone measured at the midpoint of the plate and set to 53.5% (top) and 27% (bottom) of each hitter’s height, with results shown in seconds on scoreboards and broadcasts.
- Spring training data showed about 2.6% of pitches were challenged and roughly 50–53% were overturned, with catchers generally outperforming hitters and pitchers on accuracy, so teams are refining who should trigger reviews and when to save them for higher‑leverage counts.
- The system is live in all 30 MLB ballparks after approval by the Joint Competition Committee last September, though special events at venues without Hawk‑Eye — such as the Mexico City Series, the Field of Dreams game, and the Little League Classic — will proceed without ABS.