MLB Ump Watch
The 2025 Ump Run-Factor Board: Overs, Unders, and the Men in Blue
Published
The archive keeps score on the men keeping score. These are the 2025 rolling-window run factors for home-plate umpires from our Retrosheet mirror, anything over 1.00 leaned toward offense, anything under leaned toward pitching.
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.
Where the runs flowed
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 (1.097 in 96 games) keeps the trend company.
The pitchers' best friends
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 is nearly as stingy at 0.893 over 92 games.
By the numbers
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 |
The fine print
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.
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.