The Zone of Uncertainty

If you gave every ballplayer and umpire and coach truth serum, then asked them how well they know the strike zone, how many do you think would rate themselves better than average? My estimate: Something close to “all of them.”

Which of course can’t be true. Without a concrete reason to challenge their own self-assessment, people tend to place themselves highly on mental leaderboards. In a recent YouGov survey of thousands of Americans, only 4% of respondents said they considered themselves to be of below average self-awareness. So 46% of them would be particularly floored if someone rolled out a head tap system for proving social faux pas.

Given some experience to the contrary, or understanding the prospect of a test, we become harsher judges of our own abilities. Only 15% of respondents said they were above average at running — perhaps mentally skirting the follow-up: Oh great, so what has your average mile time been recently?

MLB’s automatic ball-strike system is a challenge measured in challenges. It is transforming a broad trait like intelligence (56% above, 6% below, per YouGov) into something more specific like mathematical ability (32% above, 26% below). And its best analogy might be the first day of school, leveling up from trigonometry to calculus with a pop quiz. The basic ideas might be familiar, some will be better prepared than others, but everyone is feeling out new territory.

There are many, many avenues of inquiry that will be worth studying around ABS, though most are best left for a later date.

But today I thought we could take a look at the learning curve in its early stages. Where are baseball’s players and umpires being confronted with what they aren’t actually sure of? Where is the concrete (if invisible) reality of the newly defined zone clear to them, and where is it still a shot in the dark?

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The zone has been on a diet for years.

FanGraphs’ Davy Andrews showed last year, with a series of illuminating charts, how the more precise technology of Statcast and increased scrutiny of umpires had already combined to tighten up the strike zone over the past decade. The effect was a taller, skinnier zone and a thinner strip of toss-up territory.

The ABS system is a more strictly enforced version of the zone that was already reshaped through attention and exercise. Like Ozempic, or a corset.

The two-per-team limit on unsuccessful challenges introduces scarcity and strategic considerations, leaving the vast majority of calls unchecked in the moment, even as the ABS system hums along printing binary judgments in the background. Layer that catalog of the umpire’s trained decisions and the players’ most confident guesses on top of the answer key and you begin to shade in the parts of the zone where everyone involved might need to confront uncertainty.

Using Statcast data, which in 2026 charts pitches by the ABS zone, I compared this season to recent history using a three-year sample of 2023-25.