Ryan Lamb, 22, who plays for Guinness Premiership leaders Gloucester, hit student Gregor Paterson after he shouted that Lamb should be in the national side instead of fellow fly-half Andy Goode, magistrates were told.
Lamb, who has featured for England Saxons and is regarded as a future international regular, was fined £1,000 by magistrates in Cheltenham after pleading guilty to common assault.Prosecutor Theresa Perry said Lamb was out with friends at Cheltenham's Subtone nightclub in the early hours of 1 March when the incident occurred.
Paterson, who is a Gloucester fan and regular at the club's Kingsholm home, recognised Lamb but kept his distance. At 3.30am Lamb left the club and walked towards his taxi, followed by Paterson, 20. Paterson told police he called out to Lamb, shouting: "You should be in the England team. You're better than that Andy Goode."
Lamb said the comments he heard were of a "completely different and personal nature", Perry said. Wound up, he punched Paterson once to the mouth, causing a cut and swelling.
Paterson went to Cheltenham General Hospital where his lip was glued.
After his arrest, Lamb, from Hucclecote, Gloucester, accepted the events and said he was "remorseful".
Paul Whitcliffe, defending, said Lamb was upset at being left out of Gloucester's first team on a few occasions and had only wanted a good night out with his friends.
As well as the fine, Cheltenham magistrates ordered Lamb to pay £200 compensation to Paterson, £50 prosecution costs and a £15 victim surcharge.