The 2026 MLB season will see the full implementation of the Automated Ball Strike (ABS) Challenge System after its trial run in Spring Training last year. The rule change was voted on by the joint competition committee toward the end of last year.
The ABS system will be limited to the regular season in 2026, with postseason implementation beginning next year.
The arrival of the ABS challenge system represents the biggest change to the sport since multiple alterations were put in place at the start of the 2023 season. The pitch clock, larger bases and restrictions on shifts have all achieved the desired results of improving the pace of play and increasing offense.
A core tenet of this review system is how many challenges each team has to start the game. Each team starts every game with two challenges, and only a successful challenge is retained.
However, the rules change should a game reach extra innings. Regardless of whether a team has both their challenges remaining or zero remaining, each side is guaranteed to have one challenge in each frame during extra innings, according to Alden González of ESPN:
New wrinkle with MLB implementing the ABS challenge system for the regular season in 2026: In extra innings, teams will always have at least one challenge. So, if a team has zero after nine, it’ll get one for the 10th. If it loses it in the 10th, it’ll get one again for the 11th.
— Alden González (@Alden_Gonzalez) February 13, 2026
In other words, if a team exhausts their challenge, they will still receive another in the ensuing inning, should the game continue. If a team has challenges remaining at the start of the 10th inning, they will not get an additional one for that frame, though they will for any subsequent inning(s) if they are out of challenges at the start of it.
There are justifiable pace of play concerns with this model, as it basically guarantees at least one challenge per half-inning. However, it shouldn’t be a huge issue considering the whole replay process takes approximately 15 seconds to complete.
There is certainly room to make fixes and adjustments accordingly based on the results of this season and down the line once enough data has been gathered.
MLB challenge system works details
The home-plate umpire is still in place and responsible for calling balls and strikes on every pitch and the challenge system allows for teams to request an expedited review of those calls.
Pitches are tracked by 12 Hawk-Eye cameras set up around the perimeter of the field. If a pitcher, catcher or batter disagrees with the umpire’s initial call, a challenge can be requested by immediately tapping on his hat or helmet and vocalizing a challenge.
Only the batter, pitcher or catcher are allowed to call for a challenge. It must be requested immediately after the call, and help from the coaching staff, other players or anyone else is not permitted.
Upon review, if any part of the baseball touches any part of the strike zone, the pitch will be considered a strike.
Other aspects of the ABS system include, the strike zone for Challenge System, how ABS strike zone compares to umpires and how MLB decided on this system.
