Manchester United teammates clashed in the home dressing room after Saturday's defeat to Brighton.
United were thumped 3-1 by the Seagulls to make it a third defeat in their opening five Premier League games this season.
The Sun says captain Bruno Fernandes confronted fellow midfielder Scott McTominay in the aftermath.
While centre-backsg Lisandro Martinez and Victor Lindelof also turned on eachother as arguments raged inside the locker room.
United manager Erik ten Hag moved to try and restore order as the players' frustrations boiled over.
Ten Hag's players now face an opening Champions League clash against Bayern Munich later this week.