Players say MLB's robot umpires are shrinking the strike zone

Arizona Diamondbacks closer Paul Sewald knows that — in theory — Major League Baseball’s new Automated Ball-Strike system shouldn’t favor batters or pitchers.

In practice, he thinks one side has gained an advantage.

And it’s not the guys throwing the baseball.

“It’s what (MLB) wanted — people on base,” Sewald said. “Tough time to be a pitcher. Balls flying everywhere, you’ve got a smaller strike zone. But you just go out there and do the best you can.”

So ... is Sewald right? It depends on which numbers you want to use, but it sure seems like the strike zone has shrunk.

Walks have skyrocketed to near historic highs through the season’s first month. There’s no direct evidence ABS is the reason for the increase, but as D-backs catcher James McCann said: “Of course it is. What other rules have changed?”

MLB players have drawn a walk in 9.8% of plate appearances this season through Wednesday’s games, which would be the highest rate since 1950. The rate is likely to come down as the season progresses — pitchers usually have more trouble finding the zone during widespread chilly conditions in northern cities during March and April.

Everyone knew the strike zone would change. MLB had to re-write its definition of the zone to accommodate the shift to robot umpires. The Official Baseball Rules long described a zone stretching from the midpoint of the hitter’s torso down to the “hollow beneath the kneecap.” The new zone is more precise. It starts at 27% of a batter’s standing height and stretches to 53.5%. The ABS zone is 17 inches wide, matching the width of home plate. All pitches are measured at the midpoint of the plate.

MLB’s league-wide batting average is down slightly to .240 through Wednesday, a few ticks below the .242 rate through last year’s games in March and April. That pokes a hole in Sewald’s claim that there are “balls flying everywhere.”

If recent history is any indication, MLB rule changes can cause a lasting effect. There was a nearly 50% increase in stolen bases from 2022 to 2023 after a rules package introduced a pitch clock and limits on how many times a pitcher could make pickoff throws.

Stolen bases have remained high in the subsequent years — even after teams adjusted to the new rules.

And when MLB lowered the mound in 1969, the walk rate jumped from 7.6% to 9.1%. It dipped slightly after that but didn’t return below 8% again until 2013.

Miami Marlins manager Clayton McCullough believes the ABS issue is a different animal. He’s watching the trends and doesn’t believe the higher walk rate is here to stay.

“I think that we’ll get to a point where it gets close and stabilizes to what it’s been, where relievers are walking around 10%. Starters are going to be more around 8%,” McCullough said. “My hypothesis sitting here now early in the year is that by the time the season ends, (walk rates) will look very much like they have, say the last several seasons.”

Who knows? The next five months will tell the tale.



(AP Photo Julio Cortez)