Major League Baseball’s automated ball-strike (ABS) challenge system is set to debut this season, introducing a technological safety net to one of the sport’s most debated elements: the strike zone. For generations, balls and strikes have depended on the judgment of a human umpire positioned sixty feet behind home plate. Now, teams have the ability to challenge those calls—but the benefits will not be distributed evenly.
Under the new system, each team receives two challenges per game. A batter, pitcher, or catcher must signal the challenge within two seconds of the call, and dugouts cannot assist. If the challenge is successful, the team retains it. If not, the challenge is lost.
Simple in structure, the system has meaningful strategic implications, and the players who stand to gain the most are not necessarily the ones you might expect.
The Hitters Who Win
The biggest beneficiaries will be hitters with elite strike-zone discipline—players who take a high number of pitches and consistently avoid chasing outside the zone.
These hitters have long been vulnerable to borderline strike calls that expand the zone against them. When an umpire misses those calls, a disciplined hitter often has no recourse. The challenge system changes that.
Isaac Paredes provides a clear example. Over the past three seasons, Paredes has received more called strikes on pitches outside the zone than almost any hitter in baseball, ranking just behind Seiya Suzuki and Randy Arozarena in that category. Despite that, Paredes remains among the most selective hitters in the game, ranking in the 90th percentile in both walk rate and chase rate last season.
For hitters like Paredes, the ABS challenge system essentially acts as a correction mechanism for years of borderline calls that tilted against them.
The formula for maximum benefit is straightforward: high walk rate, low chase rate, and a high number of called strikes outside the zone. These hitters already possess a refined understanding of the strike zone. The challenge system simply allows them to act on it.
The Hitters Who Don’t
Free-swinging hitters stand to gain far less.
A hitter who frequently expands the strike zone and swings at pitches outside it rarely accumulates called strikes off the plate—because he is already swinging at them. That means fewer opportunities to challenge incorrect calls in the first place.
There is also a learning curve. Christian Walker, reflecting on his early experience with the system in spring training, acknowledged that players are still figuring out how to use it effectively.
“I’m honestly still trying to get to know it,” Walker said after successfully challenging two called strikes in the same at-bat. “I think I like it. It’s cool to have that option, but still figuring it out, for sure.”
The two-second window leaves little room for hesitation. Hitters who are unsure of the strike zone or slow to react may simply run out of time.
The Pitching Side
Pitchers are affected in different ways.
Pitchers who rely heavily on working the edges of the strike zone—those who survive by consistently painting the corners—may see some of their advantages disappear. Borderline pitches that once resulted in called strikes can now be challenged and overturned.
Conversely, pitchers who dominate hitters with pure stuff are unlikely to be affected. If a pitcher’s approach centers on swings and misses or attacking the middle of the zone, the ABS challenge system changes very little about the way he operates.
The Wild Cards
Some hitters do not fit neatly into either category.
Jose Altuve is one of them.
Statistically, Altuve profiles as a free swinger. He regularly expands the zone and makes contact on pitches outside it, which means he accumulates fewer called strikes off the plate than hitters who take more pitches.
But Altuve also possesses one of the most refined pitch-recognition instincts in baseball. Years of studying pitchers and umpires have made him extraordinarily perceptive in real time.
He may not use the challenge system frequently, but when he does, the chances are good that he will recognize the moment correctly.
For players like Altuve, the value of the ABS challenge system lies not in frequency, but precision.
The Strategic Layer
Two challenges per game may sound generous, but they can disappear quickly.
A hitter who burns a challenge early on a borderline call and loses may regret the decision later in the game when a more consequential moment arrives. Teams will likely develop internal guidelines around when challenges should be used, and players who waste them early could leave their team exposed in late-inning situations.
Ultimately, the challenge system rewards preparation. Hitters who study their called-strike data, understand umpire tendencies, and maintain a precise mental model of the strike zone will have the greatest advantage.
Those who rely solely on instinct may learn quickly that two challenges per game is not as many as it sounds.
Baseball has always rewarded discipline and punished carelessness. The ABS challenge system simply provides a new mechanism for that truth to play out.