MLB's Automated Ball-Strike Challenge System Overturns 94 Calls in First 48 Games as Robot Umpires Reshape Baseball
Major League Baseball's Hawk-Eye-powered ABS Challenge System debuted on Opening Night, giving batters, pitchers, and catchers the ability to contest ball-and-strike calls for the first time in the sport's 150-year history.
Overview
Major League Baseball opened its 2026 season with a technological first: an Automated Ball-Strike Challenge System that allows players to contest an umpire’s pitch call using Hawk-Eye camera tracking. The system debuted during the Yankees-Giants season opener at Oracle Park on March 25, and through the first 48 regular-season games, 94 of 175 challenges resulted in overturned calls, a success rate of roughly 54 percent.
The ABS Challenge System, as MLB officially brands it, represents the most significant change to on-field officiating in the sport’s modern era. Rather than replacing human umpires entirely, the league adopted a hybrid model in which plate umpires continue to make initial calls while players gain a limited right of appeal.
How the Technology Works
Twelve Hawk-Eye cameras installed around each ballpark track every pitch with accuracy to approximately one-sixth of an inch. The system measures the ball’s position against a two-dimensional strike zone tailored to each batter: 17 inches wide to match home plate, with the top set at 53.5 percent of the batter’s height and the bottom at 27 percent. The zone is evaluated at the plate’s midpoint, 8.5 inches from both the front and back edges.
When a player initiates a challenge, the result is transmitted over a 5G network and displayed on the stadium videoboard within seconds. The average review takes approximately 17 seconds, a pace designed to avoid disrupting the flow of the game.
Challenge Rules
Only the batter, pitcher, or catcher may challenge a call. Managers, bench coaches, and other players on the field are prohibited from initiating or assisting with challenges. A player signals a challenge by tapping his cap or helmet within roughly two seconds of the umpire’s call.
Each team begins with two challenges per game. A successful challenge is retained, meaning a team only loses a challenge when the umpire’s original call is confirmed. If a game extends to extra innings, any team that has exhausted its challenges receives one additional challenge per inning.
Opening Night and Early Results
Yankees shortstop Jose Caballero made the first ABS challenge in MLB history during the fourth inning of the March 25 opener. He contested a 90.7 mph sinker from Giants pitcher Logan Webb that umpire Bill Miller had called a strike. The system upheld the original call, and Caballero later acknowledged the pitch was closer than he initially perceived.
Through the first week of the regular season, catchers emerged as the most effective challengers, posting a 58 percent success rate compared with 55 percent for hitters and 41 percent for pitchers. The data prompted several front offices to instruct their pitchers to defer to catchers on borderline calls. Teams also began developing strategic guidelines, with multiple organizations discouraging challenges on 0-0 counts in favor of reserving them for higher-leverage situations later in games.
Road to Approval
MLB’s 11-member competition committee approved the ABS system on September 23, 2025, following years of testing across the minor leagues. The technology was first trialed at the independent Atlantic League’s 2019 All-Star Game and subsequently deployed in the Arizona Fall League that same year. It expanded to the Low-A Southeast League in 2021 and reached Triple-A in 2022, where it has remained in use through the current season.
During spring training in 2025, players challenged 2.6 percent of all called pitches across 288 exhibition games at 13 ballparks, with a 52.2 percent overturn rate. Fan surveys conducted during that period found 72 percent of respondents reported a positive experience with the system.
Impact on the Game
The league expects the ABS system to reduce the number of ejections related to ball-and-strike disputes, which accounted for 61.5 percent of all ejections in the 2025 season. The technology also introduces a new layer of in-game strategy, as teams must weigh the value of contesting a marginal call early in a game against the possibility of needing a challenge in a decisive late-inning at-bat.
The system is operational across all 30 MLB ballparks for regular-season and postseason games, though it will not be available for select international and exhibition contests that lack the required camera infrastructure.