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
The friendliest zone belongs to Mark Wegner, 1.125 over 71 games calling balls and strikes, where scoring has run about 12 percent above the league norm.
Adrian Johnson (1.101 in 89 games) keeps the trend company.
Dan Bellino is right behind at 1.097 over 96 games.
Where runs go to die
Brennan Miller runs the tightest environment in the sample, 0.863 across 73 games, 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 over-leaning end of the board, in one look:
| 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 |
One more thing
These factors are built on rolling three-season windows, which is long enough to mean something and short enough to notice when a zone genuinely changes.
Think of it as weather: nobody controls it, everybody plays in it, and only some people bother to check it before first pitch.
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.