CB Bucknor by the Numbers

The Reputation

CB Bucknor has been a lightning rod in baseball for years. In a 2010 ESPN survey of 100 active players, he was named the worst umpire in MLB. The viral clips have accumulated over a 28-year career: obvious misses, bewildered batters, frustrated managers.

In 2026, the ABS challenge system gave the public a new way to measure it. In his March 28 BOS @ CIN game, 8 of his calls were challenged and 6 overturned — including back-to-back called third strikes on Eugenio Suárez, both reversed. The story went national.

But anecdotes aren't data. We have 4,174 of his called pitches from the full 2025 season. Here's what the numbers actually say.

The Baseline: 3rd Worst in MLB

Across 28 games in 2025, Bucknor's accuracy was 91.02% — 3rd worst among 83 qualified umpires (behind Bruce Dreckman at 90.1% and Laz Diaz at 91.0%). The gap from the league average (92.55%) is statistically significant (p = 0.0002, Wilson 95% CI: [90.1%, 91.9%] vs league [92.5%, 92.7%]).

But accuracy alone doesn't explain why Bucknor is the umpire everyone notices. The signature stat is average miss distance: 1.34 inches — the worst in MLB. When the average umpire misses a call, the pitch was 1.13 inches from the zone edge (borderline, arguable). When Bucknor misses, it's 1.34 inches — obviously wrong to anyone watching.

This is why the viral clips happen. His errors aren't subtle borderline disagreements. They're visually egregious.

The Zone: Not What You'd Expect

You might assume Bucknor has a wildly expansive or unusual zone. He doesn't. His borderline strike rate (41.0%) is only slightly below the league median (42.7%) — ranked 31st lowest of 83 umpires. His false-strike percentage (43.5%) is almost exactly league average (42.6%).

In our zone style framework, Bucknor is a Tight Struggler: below-average accuracy with a mildly conservative zone. But his zone philosophy is unremarkable. The problem isn't where he sets the zone — it's how consistently he applies it.

One silver lining: his high-leverage accuracy (2-strike or 2+ ball counts) is 92.44% — actually 1.42 percentage points above his baseline, similar to the league average gap of +1.17pp. He doesn't melt under pressure. He's just less accurate than most umpires all the time.

The Game: BOS @ CIN, March 28, 2026

This is the game that went national. Let's look at the ABS challenges:

The Roman Anthony sequence (inning 3) is what Yahoo Sports highlighted: a called strike overturned at 2.72 inches off the zone edge, immediately followed by another challenge upheld by just 0.11 inches. The Will Benson sequence (inning 7) was equally stark: two false strikes overturned, including a 3-0 count call that was 2.41 inches off.

After all challenges were resolved, 21 wrong calls remained in the game — giving a final accuracy of 90.58% with a total challenge value of 4.08 wOBA. That's the highest single-game umpire impact in our 2026 database. The game was decided 6-5 (CIN) — the umpire's error-driven run impact potentially exceeded the margin of victory.

Was it biased?

Not clearly. Boston batters absorbed more false-strike damage (-0.814 dRE) than Cincinnati (-0.631 dRE), but all 5 missed strikes fell during CIN at-bats. Both teams were hurt by widespread inaccuracy. This wasn't a one-sided game — it was an inaccurate one.

Was it an outlier?

Not really. His BOS@CIN accuracy (90.58%) is only 0.44 percentage points below his 2025 baseline (91.02%). This was a bad Bucknor game, but not an unusual Bucknor game. That's the finding: what made national news was, statistically, within his normal range.

The Gap: Bucknor vs the Best

The contrast with the best umpire (Edwin Jimenez, 94.57%) frames the practical impact:

5.7 extra wrong calls per game. At an average challenge value of ~0.104 per wrong call, that's roughly 0.59 runs of additional game impact per game. Over a 28-game workload, approximately 16.6 extra runs shifted. Extrapolated to a hypothetical full 162-game season (which no umpire works, but for illustration): roughly 96 runs — nearly 10 wins worth of umpire-driven impact difference.

The accuracy gap (z = -6.04, p < 0.000001) is as statistically significant as it gets. The confidence intervals don't overlap. This is not noise.

What We Can't Say

• We can't say he has an extreme zone. His BSR is only mildly conservative. The problem is execution, not philosophy.
• We can't say he melts under pressure. His high-leverage accuracy is +1.42pp above his baseline, similar to other umpires.
• We can't yet say 2026 is better or worse. Only 1 Bucknor game is in our 2026 database through April 5. Anecdotal reports (Yahoo: 78% overturn rate in another game) suggest continuation, but this needs more data.
• We can't say he's uniquely bad. He's 3rd worst, not the worst. His CI [90.1%, 91.9%] overlaps with Laz Diaz [90.1%, 91.8%]. The exact ranking within the bottom 3 is uncertain.

What the Data Does Say

CB Bucknor makes more mistakes than almost any umpire in MLB, and when he does, they're visually obvious. His 1.34-inch average miss distance is the kind of error that makes batters turn and stare. His 2025 accuracy (91.02%) means roughly 13 wrong calls per game — about 3 more than the average umpire.

The ABS system didn't create this pattern. It measured it. The BOS@CIN game — the one that went viral, the one with 6 overturned calls, the one where the announcer couldn't believe what he was seeing — was only 0.44 percentage points below his season average. That's the story: the game that shocked the baseball world was a normal CB Bucknor game.

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