MLB's robot umpires overturned 54% of challenged calls in first ABS season

Major League Baseball introduced the Automated Ball-Strike (ABS) challenge system leaguewide in the 2026 regular season, allowing the pitcher, catcher or batter in each at-bat to ask for an instant replay review of a ball or strike call. According to figures reported by ESPN, players used the challenge 10,557 times across the season, an average of 4.35 per game, and the optical tracking system overturned the umpire's original call in 5,686 of those instances — a 54% reversal rate.

How the challenge works

Under the rules described by ESPN and confirmed by wire reporting carried on ClickOrlando, only the pitcher, catcher or batter involved in the pitch can request a review, and a team loses its remaining challenge once it has been wrong twice in a game. A review typically takes well under two minutes; wire reporting put the average challenge time at about one minute 25 seconds, and in the sport's first postseason-ending challenge, the review itself took 16 seconds.

Teams adjusted their use of the system as the season went on. Per ESPN's reporting, challenges rose from 3.76 per game in March to 4.61 in September, and success rates were higher early in games — innings one through three averaged a 61% success rate — than in the ninth inning, where success dropped to 40%, reflecting more cautious, selective use of challenges as a game's remaining appeals ran low.

Which teams and players got it right most often

The Cincinnati Reds led all teams with a 62% challenge success rate and the largest run-value gain from overturned calls, at +16.8 runs, according to ESPN's full-season tracking. The Los Angeles Angels (+14.0 runs) and Oakland Athletics (+12.3 runs, 60% success) followed. At the other end, the Cleveland Guardians lost an estimated 13.4 runs on unsuccessful or missed challenges and the Los Angeles Dodgers lost 8.5 runs — both clubs that reached the playoffs despite the negative tally. Pittsburgh posted the league's lowest success rate at 47%, per the ClickOrlando report.

Catchers were the most effective challengers, winning 59% of their appeals, compared with 49% for batters and 40% for pitchers, ESPN reported. Milwaukee's William Contreras filed the most challenges of any catcher, 185, winning 105 of them (57%). Philadelphia's J.T. Realmuto posted the highest success rate among catchers with at least 75 challenges, at 81%, according to the same tracking.

The first playoff game decided by a robot umpire

The system's highest-profile moment came on September 30, 2026, in Game 2 of the National League Wild Card Series between the Philadelphia Phillies and Atlanta Braves at Truist Park, as reported by Crossing Broad. With the score 4-3 in the bottom of the 10th inning and Atlanta runners on base, Phillies pitcher Andrew Painter threw an 0-2 pitch to pinch-hitter Dominic Smith that was called a ball. Realmuto immediately signaled for an ABS challenge; the review, which took 16 seconds, overturned the call to strike three, ending the game and keeping Philadelphia's series alive. Crossing Broad described it as the first time a playoff game had ended on an automated ball-strike challenge.

What the numbers suggest

A roughly even split between calls upheld and overturned — 54% reversed versus 46% confirmed — indicates that neither human umpires nor the optical tracking system dominates close ball-strike calls outright; instead, players appear to have learned over the season which specific pitch locations and game situations are worth challenging. ESPN's data showing higher success rates in early innings and lower rates in the ninth suggests teams became more selective as games progressed and challenges became scarce, rather than the technology itself changing in accuracy.