Reading striker Leroy Lita, 21, is being questioned by police in Bristol over the alleged attack in Haymarket, in the early hours of Sunday morning.
The England Under 21 striker signed for the Premiership side last summer from Bristol City for £1m.
He has been accused of leaving his alleged victim with a black eye.
An Avon and Somerset Police spokeswoman said: "A 21-year-old man from Reading voluntarily attended Trinity Road Police Station in Bristol at 8.30am today, where he was arrested on suspicion of GBH.
"His arrest follows the alleged assault of a 24-year-old man from Westbury-on-Trym, Bristol, in the early hours of Sunday morning in the Haymarket."
The Congo-born forward, who scored Reading's winner against Middlesbrough in the opening game of the season, is expected to be released on bail later.
http://news.bbc.co.uk/1/hi/england/5298340.stm