Memphis' O.J. Mayo and Tony Allen needed to be separated on Monday's charter flight after they started to fight over a card game, according to Yahoo Sports.
Mayo reportedly owed Allen money from the game and "became increasingly belligerent and antagonistic toward Allen" when asked to pay up.
After Allen went to the bathroom, Mayo continued to "berate" his teammate and Allen eventually hit the Grizzlies star.
A source told Adrian Wojnarowski that Allen warned Mayo to "watch his mouth," but Mayo "just kept going off on him."
Several players separated the two and general manager Chris Wallace confirmed the altercation in an e-mail sent to the media.
"The club considers the matter closed and will not comment further," Wallace said.