There's Already Disagreement About MLB's Robo Ump System After All-Star Game

Major League Baseball is bringing the automated ball and strike system, better known as "robo umps," to big league games, likely by the 2026 season. To test how well the system works, or doesn't work, after a trial in spring training, the league decided to use it during the 2025 All-Star Game in Atlanta.

And it already sparked a disagreement about it between the MLB Players Association and MLB commissioner Rob Manfred.

The executive director of the MLBPA, Tony Clark, said this week that he thinks the system should implement a buffer zone to stop calls from being overturned that are just barely on or off the plate. 

"Does there need to be some type of buffer-zone consideration?" Clark said. "We haven’t even started talking about the strike zone itself, how that’s going to necessarily be measured." 

Here's an example of what he's talking about: Mets closer Edwin Diaz challenged an 0-2 pitch that was called a ball against Randy Arozarena in the ninth inning, and the automated zone ruled it a strike by about a millimeter. 

Some may see Clark's point after watching that replay. Rob Manfred doesn't.

Jul 13, 2025; Atlanta, GA, USA; MLB Commissioner Rob Manfred opens the MLB Draft at The Coca-Cola Roxy. Mandatory Credit: Brett Davis-Imagn Images

Rob Manfred Doesn't Think There Should Be Buffer Zone For Robo Umps

In response, Manfred flatly rejected the idea.

"I don’t believe that technology supports the notion that you need a buffer zone," Manfred said. "To get into the idea that there’s something that is not a strike that you’re going to call a strike in a review system — I don’t know why I would want to do that."

Given Manfred can impose the system for the 2026 season unilaterally, and has already stated his intention to do so, it's ultimately his opinion that matters most. Though Clark would like to see the players have more input on how the challenge system is implemented and functions. 

"I would like to believe that at some point in time, when it’s represented to the committee and in front of players, and players offer input, that it’s actually listened to," Clark said. "I still remain hopeful that that may be the case. But our guys do have a concern with that half-inch, what that might otherwise lead to."

"There’s a lot of discussion that still needs to be had, despite the fact that (implementation) seems more inevitable than not," he continued.

Challenge systems always provide a case study in what people want out of baseball. Do you want to see the correct call made on the field at every opportunity? Or is preserving the pace and flow of the game more important? 

The ABS system will disrupt it, even just a handful of times per game. It will make the end of an inning or a walk to load the bases a bit of a "hold your breath" moment, until the time for a challenge passes. But it also makes it more likely that egregious missed calls by the home plate umpire are corrected. Clearly, Manfred wants that to include pitches that barely graze or miss the zone, without a buffer. Whether you like that or not depends on your perspective.