There will come a day, likely very soon, when baseball’s new automated ball-strike challenge system will decide the outcome of a game and purists will bemoan the rise of robot umpires.
Don’t worry, you’ll get used to it.
In much the same way the pitch timer and rules controlling infield shifts created little drama after they were introduced, ABS doesn’t interfere with the game.
The result — including a pitch’s distance from the strike zone, if it was a ball — is displayed on the scoreboard.
The system was tested in the minor leagues from 2022-25, and approved for use last September by MLB’s Competition Committee. The league could have used it to call every pitch but settled on a challenge system instead to leave the human element intact.
“You get used to it pretty quickly,” Red Sox infielder Mikey Romero said. “I like it because you can get the call right. The pace of the game doesn’t really change.”
A look at the scoreboard during an ABS challenge in spring 2025. (Tim Warner/Getty Images)
You may come to appreciate just how good major league umpires usually are at calling balls and strikes. When calls are overturned, it’s often the difference of less than an inch.
“One thing for sure, it tells us that job, for how hard that it is, they do an outstanding job. They really do,” Red Sox manager Alex Cora said. “Two hundred pitches [a game] whatever it is, and they miss five. We get on them.
“Now that we see it and we get the feedback from ABS, man, they’re the best of the best, and they keep working on it.”
Team USA’s thrilling 2-1 victory against the Dominican Republic in the semifinals of the World Baseball Classic ended on a called third strike from Mason Miller to Geraldo Perdomo that was clearly below the strike zone. ABS wasn’t used in the tournament or otherwise that game would have ended in a more equitable manner.
How could anyone be opposed to that?
It’s a historic change for baseball. Teams once prepared scouting reports on umpires based on their strike zone. One umpire would call high strikes, the next day it was something else. The strike zone was interpreted on a daily basis.
Now there’s one strike zone, the same for every game.
“It’s the ABS strike zone now,” said Red Sox game-planning coach Jason Varitek, a former catcher. “You could see it in spring training, the umpires called the same zone.”
There is one potential downfall to ABS: The entertaining spectacle of managers arguing with umpires about balls and strikes could be relegated to history’s dustbin.
Managers may still chirp from the dugout. But if it’s actually a missed call, it’s a pat on the head from being corrected.
But Cora, who has been ejected 21 times over seven seasons, does not envision peace in our time.
“At one point people are going to run out of challenges, sometimes early in the game,” he said. “When you run out of challenges it’ll be back to what we used to do.”
A sport that has spent 150 years stacking layers of strategy is about to find another dimension.
The introduction of ABS comes with plenty of fresh questions about who will use those challenges, when, and why.
It’ll be a new game within the game.
“We’re trying to be efficient or the best challenging team,” Cora said. “That’s what we’re trying to accomplish, when to do it and be successful. Don’t challenge just to challenge.”
How Red Sox players have fared in challenges during Spring Training
See the result of each challenge by offensive and defensive Red Sox challenge, along with whether the challenge resulted in a walk or strikeout being flipped and the distance the pitch was from the edge of the zone. Hover or touch pitches to see details.
HittersFieldersWillson ContrerasRoman AnthonyCaleb DurbinCeddanne RafaelaWilyer AbreuAndruw MonasterioMarcelo MayerKristian CampbellTsung-Che ChengVinny CapraJarren DuranCarlos NarváezAllan CastroMickey GasperBraiden WardEnddy AzocarCorey RosierMikey RomeroTrevor Story
Overturned
Upheld
Willson Contreras (1B)
- Chal.6
- Rev?5
- Success rate83.3%
Pitches initially called strikes:
DateBat SideReversedK/BB flipDistance2/21RYesY0.81″2/24RYes2.27″2/24RYes0.53″2/24RNo0.06″2/26RYes1.42″3/20RYes0.25″
Based on conversations with some of the Red Sox — including those who used the system during the minor league trial run — here are some of the strategies that will be in play:
Challenges are a limited resource. A team can be wrong only twice in a game before it is out completely (until extra innings). So players need to be selective about when to use them, especially early in games.
In higher-leverage spots (runners on base, especially as it gets late in the game), go for it. In low-leverage situations (early innings, bases empty, two outs), don’t bother unless it’s a clear missed call.
“The strategy is to keep your challenges for as long as you can, to have at least one by the ninth, because umpires may be more likely to expand the zone,” third baseman Caleb Durbin said. “If the umpires miss a call, you want to have that [challenge] later in the game. So you want to keep the zone as it is. You don’t want to leave it up to the umpire late in the game without a challenge.”
That means there will be instances early in a game when the umpire misses a call but nobody formally questions it. Timing is everything.
“Fans are going to see calls that are wrong that don’t get challenged and kind of not really understand why they haven’t been challenged,” said reliever Zack Kelly, an ABS veteran via Triple A experience. “But it’s because you have to pick and choose your spots. A 3-and-0 count with nobody on, that’s not a spot to challenge. Even later in games, if you have it, even if you don’t feel confident in a challenge, it’s almost kind of worth taking a shot just because of where the game is.”
Officially, hitters, catchers, and pitchers can challenge. In practice, pitchers don’t.
“I mean, it hasn’t been explicitly said,” Garrett Crochet said, “but I don’t really intend to.”
The logic is straightforward: Pitchers are far from the plate. Catchers are right there. Who has a better view of the pitch location? Catchers. Who is more likely to be swayed by the emotional desire for a strike call? Pitchers.
For that reason, pitchers rarely used challenges in the minors. That likely will continue in the majors.
Crochet has talked with catcher Carlos Narváez about an exception: when a runner is stealing a base, distracting the catcher (and the umpire), and perhaps causing a missed call.
“There’s a lot of movement, but I see where the pitch goes,” Crochet said. “The catcher doesn’t really know where it was, and the umpire doesn’t know where it was. That’s kind of the only time.”
As Durbin explained: A human-called strike zone tends to be an oval, with pitches slightly above, below, or wide often called strikes, but the corners less so. The automated zone, however, is a perfect rectangle.
So now, when a batter gets a pitch that barely nips the corner — a pitch that for his whole baseball life was usually ruled a ball — it will be an ABS strike.
“You have to be careful challenging it on the corners,” Durbin said. “With the ABS system, it just has to tip that rectangle.”
Unlike the top and bottom of the zone, which will vary depending on the batter’s height, the east and west edges will always be the same. There are challenges to be won there via zone knowledge.
“The edges of the plate are fixed,” said Parker Guinn, the Red Sox’ catching instructor. “The up-and-down piece is something that we’re continuing to try to work with them on understanding.”
Framing pitches and trying to steal strikes still will be a valuable skill, Guinn said, especially in instances when a team is out of challenges.
Through his years in Triple A, Nate Eaton noticed that when he was going good at the plate, his challenges were more successful. He literally was seeing the ball well. So he became more comfortable challenging during games/stretches when he knew he was hot. And vice versa when cold.
The ability to successfully challenge strike calls may well be a skill susceptible to slumping, just like hitting.
“If I’m going through it and I’m swinging at some bad pitches and not really feeling good at the plate, I’m going to be a little more hesitant to do that challenge,” Eaton said.
Cora said: “You don’t see the ball, you’re begging for calls.”
Eaton was among the best in the minors at challenging strike calls, Cora said, with a 78 percent success rate. Roman Anthony? Not so much, apparently.
“We got numbers from last year, and a lot of people think that there’s one guy [who] should have been good,” Cora said with a laugh. “And he was awful.”
Much like when base runners have the green (or red) light to steal a base, the same should be true of hitters for challenges.
Take Ceddanne Rafaela, for example. He swung at 42 percent of pitches outside the strike zone last year, among the most extreme rates in the majors. Conversely, Anthony swung at 20 percent, Durbin 22 percent, Masataka Yoshida 27 percent, Wilyer Abreu 29 percent. Those who are more selective should be more empowered to challenge.
“If you chase a lot of pitches, it’ll be hard for you to go ahead and challenge,” Cora said. “There’s some obvious ones.”
MLB has spent years preparing to bring ABS to the highest level. The Red Sox have used the technology in practice settings at spring training, in addition to exhibition games. Other strategies are sure to evolve once they see the rules in action.
“That,” Guinn said, “is something that we’re continuing to work through.”
It’s impossible to know what impact the introduction of ABS will have. But any fundamental change to the way the strike zone is regulated and interpreted has immense potential repercussions.
Those who have experienced the system in Triple A have little doubt about how it will tilt the hitter/pitcher seesaw in its major league debut.
“It’s definitely going to favor the hitter,” said 20-year veteran pitcher Rich Hill, who made nine starts with ABS in Triple A last year. “No doubt about it.”
The actual opportunity to challenge ball/strike calls, of course, will have an impact. An overturn that transforms a called third strike on a full count into a ball will flip a strikeout into a walk, potentially the difference between a rally-killing and rally-stoking event.
That said, the number of pitches directly impacted will be limited. Teams start each game with two challenges. They retain any challenge that is successful, but umpires are very good at what they do, as evidenced by the fact that only 49.5 percent of challenges in Triple A resulted in overturns.
Put another way: About one out of every 186 pitches in Triple A last year resulted in a challenge and overturn, with an average of 4.2 challenges and 2.1 overturns per game. But challenges alone do not define how the new system will impact the game.
In a way, ABS impacts every pitch. The three-dimensional strike zone, whose perimeter is set by the umpire’s interpretation, will be replaced by a two-dimensional, rectangular strike zone defined 8.5 inches from the front and back of the plate and with exact boundaries.
There will be no mystery about where the borders of the strike zone are supposed to lie, a fact that will change offensive approaches.
“It’s less about who’s a really good challenger, and more about, when [the strike zone] is defined the same every single night, and when hitters hone in on that, they’re going to know what to swing at,” said Worcester Red Sox manager Chad Tracy, who has witnessed the evolution of the system in Triple A since 2022. “You’re going to see more walks, more base runners. You’re going to see a little bit more OPS in general. That’s kind of what happened as we tracked it.”
Everyone agrees that the two-dimensional strike zone has been smaller in Triple A than the three-dimensional zone in the big leagues.
“The zone is smaller,” said Tracy. “It’s a fact.”
A compressed zone allows hitters and forces pitchers to funnel offerings into a narrower window. The result in Triple A has been felt in an increase in walk rate, decrease in strikeout rate, and more freedom for hitters to lean back and take aggressive hacks.
But how much has that affected offense? It’s hard to say, given that Triple A has experimented with different permutations of the full ABS system (“RoboUmps,” with all ball/strike calls made electronically) and ABS challenge system over the last four years.
Still, there are some indicators that the smaller ABS zone is permitting offense to withstand improved stuff.
In Triple A, the average fastball velocity is up nearly 1 mile per hour over the last few years, from 92.4 in 2022 (the season where 11 of 30 parks used ABS) to 93.2 in 2025 — a development that ordinarily would make life more miserable for hitters. Yet scoring in Triple A is roughly unchanged over that period, going from 4.98 runs per game in 2022 to 4.94 in 2025.
How? Pitchers have been forced to work more frequently in the strike zone, with a roughly 5 percent increase in the rate of pitches thrown in the zone. Hitters are chasing about 5 percent fewer pitches out of the zone.
The result: Despite better stuff more frequently thrown in the zone, walk rates are up about 6 percent in Triple A, while the strikeout rate is down by 2 percent. Level-wide slugging numbers have gone down slightly, but there have been more base runners and balls in play that have worked to the benefit of offenses.
That’s been the case for Triple A hitters, who are typically less disciplined and zone-precise than big league counterparts. So there’s a chance the offensive impact will be greater with ABS’s introduction at the game’s highest level.
But how much greater? We’ll soon find out.
