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.
Friendly skies for hitters
Top of the board sits Mark Wegner at 1.125 across 71 games, where scoring has run about 12 percent above the league norm.
Next in line: Adrian Johnson, 1.101 across 89 games.
Dan Bellino is right behind at 1.097 over 96 games.
Where runs go to die
At the other extreme, Brennan Miller has squeezed scoring hardest: a 0.863 factor over 73 games, where scoring has run about 14 percent below the league norm.
David Rackley (0.893 in 92 games) rounds out the pitching-friendly wing.
At a glance
Here are the top five run environments, highest factor first:
| 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
Because every factor rides a rolling three-season window, the board moves slowly and honestly: no single series, however strange, can rewrite it.
None of this is about bad umpiring. Zones are simply different, and hitters and pitchers feel those differences long before the box score does.
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.