MLB Ump Watch
Ump Watch: The 2025 Run-Environment Board
Published
Some zones are cathedrals and some are closets, and the hitters know which is which long before the numbers do. Our Retrosheet build keeps score anyway: 2025 rolling run factors per home-plate umpire, with 1.00 meaning perfectly neutral.
There are 73 qualified names in the sample, spanning about 12 percent above average down to 14 percent below, a wider spread than most fans would guess.
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 is right behind at 1.101 over 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 is nearly as stingy at 0.893 over 92 games.
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.
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.