El-Hadji Diouf has been arrested and Anton Ferdinand questioned by police following a brawl in a Manchester nightclub which left one man seriously hurt.
The Doncaster Rovers striker was arrested with five other men following the incident at The Circle Club in the early hours of Sunday morning. The fight left a 33-year-old man in hospital with injuries to his head and neck.
The man is in a serious but stable condition, a Greater Manchester Police (GMP) spokesman said.
Diouf, 31, was arrested at the scene on suspicion of violent disorder. He is believed to be one of the five men who were bailed until 23 May.
Police are investigating whether a bottle was used during the fighting.
QPR defender Anton Ferdinand, 27, was questioned under caution by police following the fight but was not arrested.
Diouf's club Doncaster Rovers were relegated from the Championship Saturday afternoon although the Senegal striker did not play in their 4-3 defeat to Portsmouth.
Diouf and Ferdinand were teammates at Sunderland between 2008-09. Ferdinand, the younger brother of Manchester United and England defender Rio Ferdinand, played in his club's 1-0 defeat at West Bromwich Albion on the same day.
The Circle Club, a members-only bar in Deansgate, attracts professional footballers from Manchester United and Manchester City as well as actors from Coronation Street.
A spokesman for GMP said: "A fight had taken place and a 33-year-old man was injured.
"He was taken to hospital for treatment to injuries to the side of his head and to the side of his neck, and he remains in a serious but stable condition.
"Six men were arrested on suspicion of violent disorder, five of whom have been bailed until May 23 pending further police inquiries.
"Another man has assisted the investigation, which is ongoing."