It was the top of the third inning during Friday’s matchup between the Phillies and the Boston Red Sox. With two outs and the bases loaded, Phillies’ pitcher Charles King entered the game to face the Red Sox’s Marcelo Mayer. Down 2-1 in the count, King pitched a sinker to the low-and-away corner of the strike zone. Originally called a ball, J.T. Realmuto immediately calls for a challenge using Major League Baseball’s new Automated Ball-Strike System. The verdict? By less than half of an inch, the pitch was a ball.
Now with a 3-1 count, King tries to get cheeky, throwing the same pitch and hoping for better luck. This time, he gets the strike call but it’s Mayer’s turn to ask for a challenge. Survey says: it’s also a ball, by less than half of an inch. Ball four, the runners advance, and the Red Sox take a 1-0 lead over the Phillies.
In 13 ballparks across the Grapefruit and Cactus Leagues, this scene is playing out similarly every game. With MLB’s Spring Training experiment underway, any pitcher, catcher, or batter can challenge an umpire’s call at any time, representing a large and long-time-coming shift to MLB action.
How The ABS Experiment Started
Everyone loves the human aspect of the game of baseball, until the umpire’s call goes against your team’s best interests. It is a tale as old as time. Add in the increasing prominence in replay rules and replay technology across the professional sports industry, and Major League Baseball began to feel the pull to experiment with baseball-specific applications.
In 2019, the first iteration of the ABS system was utilized in the independent Atlantic League. In this iteration, the ABS system had full autonomy, calling every ball and strike throughout the game, eliminating the umpire from the equation.
Taking in feedback, MLB later attempted to use the ABS system in a challenge-based system in 2022 in the Florida State League. The challenge system provided each team with a set number of challenges per game to utilize at their discretion. Both the full ABS system and the challenge system were then tested in 2023 and 2024 in AAA play.
Ultimately, the challenge system proved to be the more favorable of the two systems. Next in line to test the system? Spring Training with the Big Leaguers themselves.
How the System Works
Hawk-Eye Innovations is the company behind the ABS technology MLB is employing. The system will work by taking a batter’s height and creating a zone 26.5% tall in comparison to the player. That zone will start 27% up from the player’s feet and work up to the 53.5% mark.
For a better idea of what that will look like, Bryce Harper stands at 6-3. For Harper, the strike zone will be 19.875 inches tall and start 20.5 inches off the ground. For a shorter player, like 5-9 Rafael Marchan, the strike zone would be 18.285 inches tall and start 18.63 inches off the ground. The strike zone will be 17 inches wide, as wide as home plate.
In practice, this means the strike zone is likely smaller on the top side, as described by Jomboy here.
Each team will start the game with two challenges that can be used immediately after any pitch by either the pitcher, the catcher, or the batter. Any of them can challenge by tapping their cap or helmet and cannot consult the dugout or other players before challenging. If a challenge is successful, the team retains their challenge.
In the dugout, each team will have an iPad available to look at the ABS data for every pitch thrown. So while players will only have a limited amount of in-game challenges, they will be able to look at every pitch. Clearly the main benefit will be to learn what the system is calling a ball or strike in practice rather than worrying about percentages.
There may be some in-game applications as well. Say a team learns that an umpire is calling a lot of high pitches strikes when they were actually balls? A pitcher may use that to their advantage and feed into it while a batter might know to challenge the high pitch. Or maybe a pitcher’s curveball is shown to consistently be barely missing the plate? Then a batter would know to lay off that curveball and potentially to challenge it.
Under the challenge system, a catcher’s skills with framing pitches will still have value as well, as a team will only be able to challenge so many times in a game.
What the Phillies Are Saying
With Hawk-Eye’s system being tested in AAA the past two seasons, infielder Kody Clemens has had a bit of experience with the ABS system.
“I just like that it’s consistent. You’re not going to have an outlier ball or strike called on you,” said Clemens to PSN’s Kylee Sullengerger in 2023. “There’s a couple parts of it that I don’t like. When one seam clips the zone and it’s a strike, I hate that because, you know, you take a pitch, the full ball is outside of the plate besides one seam and you get caught on it.”
Like most veterans, Spring Training is J.T. Realmuto’s first crack at the system. Given that Realmuto is a catcher, his familiarization with the system will be that much more essential if and when the system is introduced to regular season action (not until at least 2026).
“It was definitely a different dynamic, for sure,” Realmuto said to the Inquirer. “It was nice, though, just having consistent strikes and knowing what were balls and what were strikes. I think it’s going to take a little getting used to just knowing when to challenge and when not to. But overall, so far, so good.”
What is to Come
Whether you go with the genie in the bottle or Pandora’s box, the metaphor rings true all the same: now that we have started down the ABS path, there is no going back. Pitch automation is coming to Major League Baseball in some way, shape, or form. This current iteration in the challenge system seems to be going well so far, but like all things change will likely come to it before it reaches it’s final, polished form. The earliest the system could be used in the regular season is 2026, so for now, let the experiment continue!
Mandatory Credit: Kim Klement Neitzel-Imagn Images
