Major League Baseball will introduce an automated ball-strike (ABS) challenge system beginning with the 2026 season, a move finalized after a vote by the Joint Competition Committee last September. The system, powered by T-Mobile, represents a significant shift in how ball and strike calls are determined, and follows years of testing in the minor leagues.
The ABS system isn’t a complete takeover of the umpire’s role. Instead, it will function as a challenge system. Each team will be granted two challenges per game to contest a home plate umpire’s ball-strike call. Only the pitcher, catcher, and batter will be permitted to initiate a challenge. When a challenge is made, the ABS will be used to determine the accuracy of the original call.
The implementation of ABS has been a gradual process. The independent Atlantic League first experimented with the system, nicknamed “robot umpires,” during its 2019 all-star game. Umpires initially received ball-strike calls via earpieces using TrackMan technology, retaining the ability to override the automated call if they disagreed or detected a malfunction. The Arizona Fall League adopted ABS in 2021, but the technology faced criticism for calling breaking balls strikes even when they moved outside the strike zone. Human umpires were still required to relay the automated calls, and players risked ejection for disputing them, mirroring the standard rules for ball-strike calls.
Further refinement occurred in the Florida State League in 2021, and the system expanded to five Triple-A stadiums in 2022, eventually encompassing all Triple-A stadiums by 2023. During the 2023 Triple-A season, teams utilized ABS both with and without a challenge component. When a challenge system wasn’t in place, umpires relayed the automated calls directly. With the challenge system, the ABS ruling was only invoked when a team requested a review.
MLB’s decision to adopt the ABS challenge system comes after the Major League Baseball Umpires Association (MLBUA) agreed to cooperate with the league in 2020, should MLB Commissioner Rob Manfred decide to implement the system at the major league level. Details regarding spring training trials, where players will have an opportunity to familiarize themselves with the new system, have not been released.
MLB unveiled specific guidelines for the ABS challenge system earlier this month. The league has not yet commented on potential impacts to game length or umpire evaluation.