MLB's new automated strike zone has created a massive unintended consequence for hitters and pitchers

The introduction of Major League Baseball’s automated balls and strikes challenge system was expected to change the sport in 2026. For the entire history of the game, players and managers had complained about missed calls at home plate, with arguments and on-field disagreements commonplace. 

And suddenly, for the first time ever, they could do something about it. 

If catchers, pitchers, or hitters believed an umpire missed a call, they were suddenly allowed to challenge it. Two challenges per game, with more if an individual challenge proves successful. 

Even in just the first month of the season, this new practice has heavily impacted the sport. Inning-ending calls have been overturned, giving hitters another opportunity that, in some cases, has led to game-changing home runs. Pitchers have benefited from catchers getting them out of innings by turning a ball into a strike with a well-timed challenge. 

But that’s all obvious. ABS though, has also created a completely unexpected change that’s significantly impacted both hitters and pitchers.

Walks have exploded under new ABS system

With the introduction of challenges, MLB had to essentially redefine the strike zone to ensure that the tracking system would consistently and accurately measure what actually is a strike or ball. As such, they created a new version of the zone that was based on a player’s specific characteristics.

According to the rule book, "The strike zone will be a two-dimensional rectangle that is set in the middle of home plate with the edges of the zone set to the width of home plate (17 inches) and the top and bottom adjusted based on each individual player’s height (53.5% of the batter’s height at the top and 27% at the bottom)." 

How does this differ from the previous definition? Ben Clemens at FanGraphs measured the change, relative to the 2025 regular season, and found that the zone has shrunk at the top of the zone and on the edges of the plate. 

How has this played out in practice?

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Well, the new strike zone and the obvious embarrassment of having a call overturned has changed how umpires call balls and strikes. With few exceptions, it seems as though they’ve become more stingy with called strikes, and the data bears that out. 

The league-wide walk rate in 2025 was 8.4%, and from 2021 to 2025, it never went below 8.2% or above 8.7%. Thus far in 2026? The walk rate is up to a whopping 9.6%. That is, by far, the highest walk rate of any full season over the past decade.

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Essentially, the league redefined the strike zone to make it a bit smaller than the zone previously used by umpires. Umpires, afraid of being overturned, or at least, more aware of the new zone and its limitations, have been calling fewer strikes. Hitters, no doubt instructed by their teams and aware of this new shift, have been taking more pitches. 

All these factors combined lead to more walks. A 1.2% increase year-over-year is massive in a sport as consistent as baseball.

What’s equally interesting though, is that while on base percentage league-wide is .322, the third-highest figure since 2016, because hitting has become so hard thanks to the increase in velocity and pitch development, batting averages are the lowest they’ve been over the last decade.  

So ABS changed the strike zone, making it smaller than in years past. Umpires adjusted, calling fewer strikes, hitters realized it and became more patient in the process, and now walks are the highest they’ve been in a decade. Now the question becomes, will pitchers adjust back and throw more strikes, even if it risks more hard contact. Just one of many changes brought in by MLB’s attempt to make the game better.