Baseball's newest rule isn't a gimmick. The first weekend of the Automated Ball-Strike Challenge System (ABS) produced 78 batter challenges and 97 pitcher and catcher challenges across the league. But what came back from the machine was clarifying in ways nobody fully anticipated: Nearly half the calls were wrong.
Batters won 42.3 percent of their challenges opening weekend. Pitchers and catchers did even better, overturning 62.9 percent of the calls they disputed. Add it up, and you're looking at a system that, in its first weekend of existence, confirmed what hitters and pitchers have been arguing at home plate for decades: Human umpires miss a lot of borderline pitches, and now 12 Sony-owned Hawk-Eye cameras, the same tracking technology powering Statcast, is keeping score.
And the early returns don’t just show how often umpires are wrong, they also show how quickly ABS is becoming a strategic advantage. Here's what the data says.
The teams treating challenges like a resource are already ahead
If one team served as the proof of concept for how ABS challenges should work, it was Cincinnati. The Reds challenged six pitches opening weekend and got every single one overturned. Six for six. Two of those challenges converted called strikeouts into balls, extending at-bats that would have ended. One even flipped a called ball into a strike, demonstrating that the system cuts both ways.
Their net challenge benefit of +4.4 above expected isn't just good, it's the best in baseball through the first weekend, And it wasn't built on obvious calls. Savant's expected challenge model accounts for pitch location and game situation. When Cincinnati challenged, they were challenging the right pitches.
The Cubs and Giants also went perfect on their challenges, though in smaller samples. The early picture of who's using the system intelligently is starting to form.
The biggest mistake teams are making is when they challenge
The Cleveland Guardians and Atlanta Braves tell the opposite story. Cleveland challenged five times and won zero. Atlanta challenged four times, won zero. Combined, those two teams burned nine challenges and came away with nothing, dropping 3-2 and 3-1 expected challenge gains below projection respectively.
This matters in ways that go beyond the box score. Look at when challenges are being used across the league: Batter challenge rates nearly triple from the 1st inning (1.7%) to the 9th (5.8%). That isn't coincidence. Teams still holding challenges late in games are deploying them deliberately, in high-leverage situations, after nine innings of watching how the umpire is calling the zone. That is a calculated strategy.
The early-inning challenge is more likely to be emotional. A hitter sees a called strike he disagrees with in the second inning and throws up a challenge on instinct. Sometimes he's right. Often he isn't. The teams winning this part of the game are the ones treating their two challenges like a late-inning bullpen arm: something you protect until the moment actually calls for it.
Cleveland and Atlanta didn't just lose challenges on bad reads. They lost the ability to protect themselves in the 8th inning of a close game. That's the cost nobody talks about when a challenge fails.
Full counts are a trap for hitters
Here's where ABS gets strategically complicated. Across the first weekend, batter overturn rates weren't uniform. They swung dramatically based on count and situation, and the pattern reveals something important about how this system will be gamed, abused and eventually mastered.
With the bases loaded, batters won 70 percent of their challenges. Fielders won 85 percent. Both sides, under maximum pressure, were challenging the right pitches. That makes sense: With bases loaded, nobody throws a challenge away.
Full counts tell the opposite story. Batters challenged called third strikes on 3-2 counts and won only 26 percent of the time. That's the worst overturn rate of any count situation in the first weekend. The instinct is understandable: A called third strike to end an at-bat feels wrong, so you throw up the challenge. But the data says batters are misjudging the zone on full-count pitches more than any other situation, burning challenges at a losing rate precisely when they feel most certain.
Twelve strikeouts were reversed to balls across the weekend. Six walks were flipped to strikes. The 2:1 ratio favoring hitters on outcome-altering calls is real, but the full-count breakdown suggests some of those batter challenges are emotional rather than analytical. Teams that learn to sit on their challenges in full counts, waiting for the 2-strike pitch earlier in the at-bat where they're winning 34 percent and saving challenges for higher-confidence situations, will extract more value from the system than teams challenging reflexively.
The best hitters are already adjusting to the system
Among individual batters, Mike Trout leads the majors with four challenges through the opening weekend, converting three. His net benefit of +1.49 above expected ranks among the best for qualifying batters. Whatever preparation the Angels did for ABS, Trout absorbed it.
Roman Anthony of Boston challenged three times as a batter and won two, converting called strikeouts back into live at-bats. The system cut both ways on him though: In one plate appearance, a challenged ball call was flipped to a strike against Anthony. At 21 years old, he's already learning what ABS giveth, ABS can also taketh away.
Eugenio Suarez and Heliot Ramos each went 2-for-2, both converting two strikeouts to balls. Suarez has always had a good sense of the zone. Ramos is proving he does too.
The Angels as a team led the league with seven challenges but converted only three (42.9%), landing right at the league average with a net benefit barely below zero. Volume without accuracy gets you nowhere under this system.
Pitchers and catchers are winning differently
The catching team data tells a rougher story for pitchers. Boston's staff was challenged six times and lost all six, with two called strikeouts converted to balls. The Yankees and Nationals were overturned every time they were challenged, though in smaller samples. Fielders with one challenge remaining won 83% of the time, the highest overturn rate of any subgroup in the first weekend, suggesting pitchers and catchers are holding their challenges for pitches they're genuinely confident about. There may be more of a conversation here about pitch framing.
The teams holding up best on the pitching side are the ones not getting challenged at high rates, which is its own signal. When batters aren't challenging your pitchers, the calls are landing where they should.
The early edge isn’t accuracy, it’s discipline
There's a temptation to over-read 175 combined challenges across one weekend. The sample is real but small, and overturn rates will stabilize as teams and players learn which situations are worth disputing and which ones bleed challenges dry.
What won't stabilize is the underlying finding. At 42% on batter challenges and 63% on pitcher challenges, the first weekend of MLB confirmed that a meaningful share of contested calls at the plate were landing outside the zone. The system didn't reveal this as a scandal. It revealed it as a baseline.
But the more interesting story isn't the overturn rate. It's the emerging split between teams that understand ABS as a strategic resource and teams that are treating it as a real-time grievance mechanism. Challenge in the 2nd inning because a pitch felt wrong and you've spent an asset you can't recover. Save that challenge, watch the umpire work, and deploy it in the 9th with a runner on second: now you've used the system the way it was designed to be used.
The full-count batter problem, the loaded-bases accuracy spike, the late-inning challenge surge from teams disciplined enough to still have challenges left? All of it points to the same conclusion: ABS isn't just an accuracy tool. It's a strategic layer that rewards discipline and punishes reflex. It appears some teams have already learned that.
All data via Baseball Savant ABS Challenge System metrics