Reading striker Leroy Lita has been arrested on suspicion of grievous bodily harm.
The 21-year-old is being questioned by police in Bristol after allegedly headbutting a man during a night out in Bristol.
He has been accused of leaving his alleged victim with a black eye in the early hours of Sunday morning.
"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," said an Avon and Somerset Police spokeswoman.
"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."
Reading also confirmed that the club had spoken with the police.
"We are aware of the reported incident and we are in contact with Bristol police," said a club spokesman.
"We have no further comment to make at this stage."
Lita, who has featured in all three of Reading's Premiership games so far this season, is expected to be released on bail later on Wednesday.