On September 24, 2025, Major League Baseball's Joint Competition Committee voted to bring the Automated Ball-Strike (ABS) Challenge System to the big leagues for 2026. After more than a century of human umpires calling every pitch, baseball was about to change in a big way.

The decision wasn't sudden. MLB had been testing automated strike zone technology in the minor leagues since 2019. They refined the system through thousands of games and millions of pitches. By 2025, they had enough data and enough confidence to take it to the majors.

But this isn't about replacing umpires with robots. The ABS Challenge System is a hybrid. It keeps the human element while adding technology as a safety net. And as the 2026 season gets closer, teams are just starting to understand what this means.

How the ABS Challenge System Works
Under the new system, home plate umpires still call every pitch like they always have. But now each team gets to challenge up to two calls per game. If a challenge is upheld and the umpire's call gets overturned, the team keeps its challenge. If the challenge fails, they lose one.

Only the pitcher, catcher, or batter can challenge a call. They do it by tapping their cap or helmet right after the umpire makes the call. It has to happen immediately. Players can't get help from the dugout or other players before challenging.

In extra innings, teams that run out of challenges automatically get one more when a new inning starts.

The technology behind all this is Hawk-Eye. That's a system of twelve high-speed cameras set up around the field. These cameras track the ball with incredible precision. We're talking a margin of error less than one-sixth of an inch. The system determines whether the pitch passed through the strike zone.

Once a challenge happens, the home plate umpire announces it to the crowd. The scoreboard shows an animation of the pitch's path. The whole thing takes about 13 to 14 seconds on average.

The Strike Zone Redefined
Here's where it gets interesting. The ABS strike zone is not the same as the rulebook strike zone.

 Instead of using vague descriptions like "the midpoint between the shoulders and the top of the pants," the ABS system uses math. It's based on each player's measured height. During spring training, every player gets measured. The system calculates their personal strike zone from there.

The top of the zone is set at 53.5 percent of the player's height.

The bottom is set at 27 percent of the player's height.

The zone is 17 inches wide—the width of home plate. It extends 8.5 inches from both the front and back edges of the plate toward its center. This creates a two-dimensional vertical plane instead of a three-dimensional box.

This is a big departure from how we used to think about the zone. In the past, a pitch could "catch" the zone by clipping the front edge of the plate. Even if it was way outside by the time it reached the catcher's glove. Under the ABS system, the pitch has to pass through that defined plane at the right depth. The zone is smaller, more precise, and more consistent.

 The Shrinking Zone: What the Data Shows
One of the biggest effects of the ABS Challenge System is that it shrinks the strike zone. Especially at the top and bottom edges.

According to MLB's own data, umpires have historically called strikes as high as 55.6 percent of a batter's height at the top. And as low as 24.2 percent at the bottom. The ABS system sticks strictly to 53.5 percent and 27 percent. Those few percentage points mean pitchers are losing real estate.

Rich Hill experienced this firsthand. The veteran lefty pitched in Triple-A for the Kansas City Royals in 2025 before getting called up. His take on the challenge system was blunt.

"The top part of the zone does not exist," Hill told the Boston Globe in January 2026. "Players were telling me that if I throw a fastball at the top of the zone, which I've done my whole career, they said, 'Rich, if it's belt or above, I'm taking it.' That fastball just above the belt was a strike over the last 100 years. But the top part of the zone gets shrunk down."

Hill's observation matches up with data from minor league testing. In Triple-A games using the ABS Challenge System, pitchers who relied on high fastballs saw their walk rates go up. Hitters became more selective. They learned fast that pitches at the letters—once routinely called strikes—were now safely outside the zone.

 The Expanded Corners: A Gift for Command PitchersIf the ABS Challenge System takes away the high and low edges, it gives back something just as valuable. The corners.

Traditionally, umpires have called the strike zone with rounded edges. They'd deny pitchers strikes on pitches that clipped the black but didn't pass through the heart of the plate. Framing became one of the most valuable skills for catchers. Because umpires were so inconsistent on corner pitches.

Under the ABS system, framing doesn't matter. If the pitch crosses the plate within the boundaries, it's a strike. End of story.

This has huge implications for pitchers with elite command. Greg Maddux—the Hall of Fame righty and maybe the greatest command pitcher in modern history—thinks the ABS Challenge System will reward precision like never before.

"It just seems like pitchers nowadays are creating so much spin rate and velocity and all that stuff that command has kind of gotten pushed aside a little bit," Maddux said. "I think there's a place for both stuff and command, to be honest with you. It'll be nice with the challenge system to see some of the command guys getting a little bit more of a look than just the stuff guys."

Maddux's point matters. For the past decade, baseball has been dominated by guys who throw hard and generate movement through high spin rates. Command—the ability to consistently locate pitches within inches of a target—has been undervalued compared to raw stuff.

The ABS Challenge System might reverse that. Pitchers who can dot the black on the inside and outside corners will get rewarded more reliably. Those who rely on deception, changing speeds, and hitting precise spots will have an edge over guys who just rear back and throw as hard as they can.

 The Red Sox Offseason Strategy: Betting on Command
No team seems to have embraced this shift more deliberately than the Boston Red Sox.

Great article by Alan Speier Red Sox look to be in command right from the start in 2026 with MLB’s implementation of the ABS
Note: Diamond Echos already had most of the Strike Zone article completed. Alan’s ABS 2026 article pushed me to finish it for this week. It’s great read.

This offseason, the Red Sox made two big additions to their rotation. Sonny Gray via trade. Ranger Suarez as a free agent. On the surface, these moves didn't make sense. Boston has recently preferred power pitchers with triple-digit velocity.

Gray stands 5-foot-10 and averaged 92 miles per hour on his fastball in 2025. That put him in the 16th percentile among MLB pitchers. Suarez, at 6-foot-1, sat at 90.5 miles per hour. That's the 7th percentile.

But both pitchers share something that might be way more valuable in 2026. Elite command.

"If you have really good command of your pitches and are able to mix them well, you don't really need 100 miles per hour," Suarez said. "That's kind of what I do. That's what's given me the most success."

Craig Breslow, Boston's chief baseball officer, was clear about the connection between the Red Sox pitching strategy and the ABS Challenge System.

"Nobody has yet figured out how to teach command," Breslow said. "Command got people out long before velocity did. It tends to be pretty sticky. While it's really difficult to influence, it is lasting. We always think about ABS from the standpoint of catching and how do we value receiving. We appreciate far less the impact on pitchers who are consistently able to not just get the call that is two inches off the plate, but actually execute the pitch that is a half an inch off."

Breslow's comments show a bigger shift in how teams evaluate pitching talent. Framing used to be a premium skill for catchers. Under the ABS system, it'll be worth less. Borderline pitches will get called correctly no matter how they're received. But command—the ability to execute pitches on the edges with precision—will become more valuable than ever.

Hill, who's pitched in both traditional and ABS environments, thinks Boston's strategy is smart.

“There will be more emphasis on being able to pitch and not just throw, but changing speeds," Hill said. "This is what the ABS is going to be able to do. Guys are going to have to be an ultimate artist of deception and creativity, get more ground balls, as Suarez and Sonny will. Great move by Boston to be able to kind of see the future and make a decision on that."

 The Free Agent Market: Winners and Losers
The ABS Challenge System is already changing how teams evaluate free agent pitchers.

According to one agent quoted in the Boston Globe, multiple teams expressed doubts about his client. A pitcher with a long track record of major league success. The concern was how the new system would affect his effectiveness.

 "I keep hearing BS about the ABS system," the agent said. "We think ABS will really hurt him because he works off the edges of the zone so much."

The concern makes sense. Pitchers who've built careers around getting hitters to chase pitches just outside the zone might struggle. Especially those who rely on backdoor breaking balls or high fastballs above the letters. Their margin for error could shrink significantly under the ABS system.

This has created a new calculation for front offices. Teams are asking: Will this pitcher's skill set translate to a world where the strike zone gets called with perfect precision? Or will losing those umpire-given strikes at the edges expose weaknesses that were hidden by human inconsistency?

 The Minor League Laboratory: Lessons from Testing
The 2026 ABS Challenge System didn't just appear overnight. It's the result of years of testing and refinement in the minor leagues. MLB tried different versions of automated strike zone technology to figure out what would work best.

The journey started in 2019. The independent Atlantic League became the first professional league to use a fully automated strike zone. No umpires calling balls and strikes at all. Just a computer system relaying calls to the home plate umpire through an earpiece. The results were mixed. Players and fans found it jarring. The strike zone felt off.

The problem was that MLB had programmed the system to enforce the rulebook definition with perfect precision. But the rulebook zone didn't match what players, umpires, and fans expected as the "real" strike zone.

By 2023, MLB shifted to the challenge system model. Teams could appeal umpire calls instead of replacing umpires entirely. This hybrid approach worked much better. Players liked having technology as a safety net without losing the human element. Umpires stayed central to the game's flow.

Spring Training 2025 was the final test. The ABS Challenge System got used in select games. The data looked good. Teams averaged about four challenges per game. That's 2.6 percent of called pitches. Challenges took an average of 13.8 seconds. The overturn rate was 52.2 percent overall. Catchers were most successful at 56 percent. Hitters at 50 percent. Pitchers at 41 percent.

Most importantly, 72 percent of surveyed fans had a positive view of the ABS Challenge system. Only 10 percent viewed it negatively.

By September 2025, the Joint Competition Committee felt confident enough to approve it for the 2026 regular season.

 What 2026 Will Tell Us
The 2026 season will be a laboratory. For the first time, the ABS Challenge System will operate at the highest level of professional baseball. Under the brightest lights. With the most talented players in the world.

The questions are endless. Will pitchers with elite command thrive like Maddux and Breslow predict? Will power pitchers who rely on high fastballs and chase pitches struggle to adapt? Will hitters become more selective and drive-up walk rates? Will the loss of framing hurt elite defensive catchers? Or will new skills emerge as replacements? Maybe the ability to manage challenges strategically?

And maybe most importantly: Will the game itself feel different? Will fans even notice the change? Or will the ABS Challenge System just fade into the background as another part of baseball's infrastructure?

The answers will come during the season. But one thing is certain. The strike zone—that invisible and contested piece of real estate—has been redrawn again. And this time, the change isn't driven by committees and rulebooks. It's driven by cameras, algorithms, and technology.

Baseball is still baseball. But the zone, at last, has been defined with precision.