During Tuesday's wild-card game between the Reds and the Pirates, police were called to a right field bar area and found people screaming and threatening each other, Sgt. John Fisher said at a Wednesday news conference.
Dallas Latos, wife of the Reds' pitcher, was involved in the altercation, and messages appeared on Twitter saying a Pirates fan punched her in the head several times, the Pittsburgh Tribune-Review reported.
Latos wrote a Twitter post saying a "huge man" cursed and threatened her, and claimed "his chick" attacked her.
Fisher said Latos declined officers' offer to have medics treat her, and that she had no visible injuries.
No arrests were made after the fight, police said. Pittsburgh won the game 6-2 to advance to the playoffs for the first time since 1992.