Liverpool midfielder Steven Gerrard launched a volley of uppercut punches at a man in a row over music, a court heard on Tuesday.
The England international "totally lost it" and attacked Marcus McGee, 34, "with the style and speed of a professional boxer" in a bar brawl, it is alleged.
Gerrard was at the Lounge Inn in Southport, Merseyside on December 29, out with a party of friends including former Toon manager Kenny Dalglish, 58.
But trouble flared when Mr McGee refused to hand over a card controlling the CD player.
The victim was in charge of music for the venue after being given the card to pick songs for a staff party in an adjacent room to Gerrard's group.
David Turner QC, prosecuting, told Liverpool Crown Court Gerrard asked McGee for the card, saying: "Here y'are lad. Give me that lad."
Turner said: "Mr McGee took offence at his attitude and the expression 'lad' and he refused.
"Not many people on Merseyside, or indeed anywhere else, would refuse a request from Steven Gerrard but Mr McGee did.
"There can be no doubt that this refusal astounded Steven Gerrard.
"He walked away back to his party but the CCTV shows how much his mood had changed.
"He was no longer the centre of that high-spirited party.
"He was clearly walking around pondering, musing over what had happened - about the man who said 'no' to Steven Gerrard."
Several minutes later CCTV showed Gerrard returning to the victim who was sitting alone at the bar and allegedly confronting him with the words: "Who the f*** do you think you are?"
McGee stood up and the pair were head to head, Turner said, "in the sort of hostile confrontation that is often seen between professional footballers".
The barrister added: "Steven Gerrard had clearly lost his cool: he was angry with Marcus McGee."
The situation attracted Gerrard's friends.
One, John Doran, who has admitted affray, pushed McGee away but "could not resist following through with his right elbow into Mr McGee's face", said Turner.
"We say at this stage Gerrard totally lost it.
"Almost immediately after the blow from John Doran, in fact within seconds, Steven Gerrard joined in the attack with a succession of well aimed uppercut punches delivered with the style and speed of a professional boxer rather than a professional footballer."