OBR 6.02(c) · OBR 6.02(d)
Foreign substances and pitcher checks
Pitchers may not apply any foreign substance to the ball, deface it, or have anything sticky on their hands, glove, or uniform. Umpires inspect pitchers between innings, and a violation means immediate ejection — plus a suspension under MLB's discipline policy.
Key points
- The rosin bag behind the mound is legal, but it may only be applied to the hand.
- Inspections happen between innings or when an umpire suspects something; a pitcher can be checked at any time.
- The rulebook penalty is ejection. The 10-game suspension comes from MLB's enforcement policy, not the OBR itself.
- Sunscreen, sweat, and rosin mixed together have been the gray area — enforcement tightened starting in 2021.
In a game
Umpire stops a reliever on the mound and examines his glove and belt between innings.
Ruling · A routine inspection. If a foreign substance is found, the pitcher is ejected on the spot and the bullpen has to cover the game.
Why it moves the scoreboard
An ejected starter or closer changes the entire pitching plan mid-game — bullpen usage, matchup edges, and late-inning run prevention all shift.
Related rules