Liverpool have begun an immediate probe into the pitch invader who banged into Andy Robertson and provoked the ire of manager Jurgen Klopp.
The Reds thrashed bitter historical rivals Manchester United 7-0 at Anfield on Sunday.
But the evening was slightly soured when a fan ran onto the field after the seventh goal, slipped and fell headlong into left-back Andy Robertson.
Robertson held his ankle in pain after the incident, with Klopp raging at the supporter as he was taken away by stewards, for risking injury to one of his players.