DeMarco Murray has been fined for using the crown of his helmet to hit Philadelphia Eagles defensive end Damion Square.
The Dallas Cowboys running back was not penalised on the play during the final game of the regular season, but the NFL has fined him $21,000 (£12,800) for the hit.
The league controversially banned players carrying the ball from initiating contact with the crown of their helmets during the owners' meeting last March.
The Cowboys lost the game, missing out on the playoffs for the fourth season in a row in the process.
