Derek Thomas
22 games graded behind the plate.
Derek Thomas called 92.8% of taken pitches correctly in the 2026 regular season — 37th of 81 plate umpires with a full season’s sample. League rate: 92.8%.
3,210 correct of 3,458 graded takes (92.8% ± 0.9, 95%). Best game 96.7% · worst 88.5%. Grade is accuracy on taken pitches vs the rulebook zone; ABS is the Automated Ball-Strike System challenge record (how often the robots overruled the call).
What we can't say about Derek Thomas
This season is 3,458 graded takes, which puts Derek Thomas's overall accuracy at 92.8% ± 0.9 (95% interval). That is a real measurement against a league spanning about four points end to end. It is not enough for anything finer, and here is the arithmetic rather than our word for it:
- how the zone moves with two strikes — about 692 takes, so ±1.9 points. (the league-wide two-strike effect is about 1 point in 2026.)
- any single corner of the zone — about 288 takes, so ±3.0 points. (corner cells are where umpires actually differ.)
- whether one pitcher is called tighter than another — about 58 takes, so ±6.6 points. (a given pitcher is worked once or twice a season.)
And a note on the number itself: an accuracy figure is a rate plus a convention for what counts as a miss. Ours grades every taken pitch against the rulebook zone as the feed reports it. Others are more forgiving — UmpScorecards counts a call wrong only when the pitch was at least 90% likely to be a strike — so two sites can print the same percentage about the same umpire and not mean the same thing by it. How the grade is built.
The overturn rate is a different kind of number and does not belong beside the grade: it is accuracy on the 93 pitches players chose to challenge, which are the pitches they already believed were wrong. 93 is enough to print it with its own denominator, which is what we do — but it still ranks umpires by how often they are appealed, not by how often they are right.
The road to the plate
Derek Thomas
A Cedar Rapids kid who took up umpiring for side money and climbed all the way to the major leagues.
Derek Thomas grew up in Cedar Rapids, Iowa, and graduated from John F. Kennedy High School in 2009. He played three years of college baseball at Lewis University near Chicago, and when that playing career ended, he was looking for a full-time job. Umpiring started as a way to earn money on the side — something to do while he figured out what came next. Then someone suggested he attend umpire school, and the side job took a different turn.
In January 2014 he traveled to Florida for umpire school. He performed well enough to earn an assignment in the Arizona Rookie League, and his professional umpiring career began that same year. By his third professional season, in 2016, Thomas was assigned to the low-A Midwest League and was selected as the home-plate umpire for the league's all-star game. The assignment brought family and friends to the stands, cheering when his name was announced.
Thomas has said that being a former player helped somewhat, but he credited his umpire school instructors for teaching the necessary skills. He noted that umpires who never played baseball can still become very good at the work — the training, in his view, mattered more than the playing days. We have graded 14 of his home-plate games this season for the record on this page.
He umpired his first major league game on April 23, 2023, worked 85 MLB games in that rookie season, and through 2026 has recorded 14 career ejections across 356 total major league games. He works behind the plate as an active major league umpire.
Reporting: Baseball-Reference.com, The Gazette, Baseball Almanac. Umpire data: MLB StatsAPI, via the Fever engine.
By the Desk · filed 2026-07-24 — the profile reads as of its filing; the grading record above is live · every fact in this piece comes from a sourced research pack and clears an independent fact-check, and nothing is edited after filing.
The games
| Game | Grade | Favor | ABS | Blue Note |
|---|---|---|---|---|
| STL @ MIL2026-09-27 | C+ | 0.2 STL | 2/3 | If it was close, it was a strike. The hitters noticed. |
| CIN @ ATL2026-09-23 | D | 0.7 ATL | 2/4 | You had to throw it down Broadway to get the call. |
| PIT @ CHC2026-09-11 | C+ | 1.3 CHC | 3/4 | Somebody's pitching staff sent a thank-you note. |
| TB @ TEX2026-09-06 | B- | 0.9 TEX | 4/7 | A few he'd want back, and the grade says so. |
| SEA @ BOS2026-09-02 | A- | 0.2 SEA | 1/4 | Called a fair game and let the players decide it. |
| LAA @ BAL2026-08-06 | B | 0.2 BAL | 0/2 | A small strike zone, generously enforced for the offense. |
| PHI @ BAL2026-07-31 | B- | 0.2 BAL | 1/3 | Pitchers earned every strike the hard way. |
| SEA @ TEX2026-07-27 | B+ | 0.3 TEX | 1/3 | Nothing that'll trend, and on this beat that's a compliment. |
| DET @ CHC2026-07-22 | B+ | 1.4 CHC | 1/3 | The zone leaned, and the ledger noticed. |
| MIA @ MIL2026-07-18 | B | 0.4 MIA | 5/8 | This one went to video review more than most. |
| SEA @ TB2026-07-12 | B+ | 0.6 TB | 2/4 | The kind of night where the umpire is the least of the story. |
| BAL @ LAD2026-06-21 | B+ | 1.2 LAD | 0/3 | One dugout got the friendlier version of the evening. |
| MIN @ TEX2026-06-15 | A | even | 1/5 | If umpiring had a highlight reel, this wouldn't make it. That's the compliment. |
| DET @ TB2026-06-03 | B | 0.3 DET | 2/4 | Squeezed the edges; the hitters didn't mind at all. |
| SD @ WSH2026-05-30 | C+ | 0.6 WSH | 4/7 | Pitchers found a little extra real estate. |
| NYM @ MIA2026-05-23 | A- | 0.3 NYM | 1/3 | Nothing that'll trend, and on this beat that's a compliment. |
| MIL @ CHC2026-05-18 | A | 0.2 MIL | 2/3 | Solid and unspectacular — exactly what the job asks. |
| LAA @ KC2026-04-25 | C | 0.1 KC | 1/5 | Expanded the plate a touch past its 17 inches. |
| HOU @ CLE2026-04-21 | A | 0.5 HOU | 2/4 | An honest evening's grade: nothing loud, nothing missed by much. |
| MIL @ MIA2026-04-17 | A- | 0.8 MIA | 1/6 | Reliable as a Tuesday: no complaints, no headlines. |
| MIN @ TOR2026-04-12 | A | 0.9 TOR | 1/3 | Called a fair game and let the players decide it. |
| STL @ WSH2026-04-07 | B | 1.4 WSH | 1/5 | Somebody's pitching staff sent a thank-you note. |
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