MLB Ump Watch
Ump Watch: The 2025 Run-Environment Board
Published
Every home-plate umpire carries his own strike zone, and over enough games that zone becomes a run environment you can measure. From our Retrosheet archive, these are the rolling three-season run factors through 2025, where 1.00 means dead-league-average.
The sample covers 73 umpires with enough games behind the plate to matter, and the environments range from roughly 12 percent above league average at one end to 14 percent below at the other.
The offense-friendly zones
Mark Wegner owns the most hitter-friendly environment in the sample: a 1.125 run factor across 71 games behind the plate, where scoring has run about 12 percent above the league norm.
Adrian Johnson is right behind at 1.101 over 89 games.
Dan Bellino is right behind at 1.097 over 96 games.
The tight zones
The stingiest zone belongs to Brennan Miller: 0.863 over 73 games behind the plate, where scoring has run about 14 percent below the league norm.
David Rackley is nearly as stingy at 0.893 over 92 games.
At a glance
The five most offense-friendly zones in the sample:
| Umpire | Run factor | Games |
|---|---|---|
| Mark Wegner | 1.125 | 71 |
| Adrian Johnson | 1.101 | 89 |
| Dan Bellino | 1.097 | 96 |
| Mike Muchlinski | 1.093 | 86 |
| Chris Guccione | 1.091 | 79 |
Worth remembering
Method matters here: each factor is a rolling three-season sample, so one wild week cannot vault a name to the top of the board, and a single quiet month cannot bury one.
The spread is the story: a few points of run factor is the difference between a park that plays over and one that plays under, except this park travels with the umpire from city to city.
These are historical tendencies from seasons past, not tonight's assignments, treat them as trivia about the shape of the sport, not a betting signal on any specific game.