Manchester City have suspended Joey Barton for the rest of the season after he hit team-mate Ousmane Dabo in training, BBC Sport understands.
Barton's agent claims the player was defending himself
Dabo had to go to hospital after suffering injuries to his mouth during the incident at Carrington on Tuesday.
Barton's agent, Willie McKay, was responsible for bringing Dabo to City from Lazio in June 2006.
He told BBC Sport: "As far as I've heard, Joey was defending himself. But because it is Joey it makes headlines."
McKay added: "It happens on training grounds all over the country, from Chelsea to Yeovil."
City are currently refusing to confirm the identity of the player who has been suspended.
A club statement read: "We can confirm that a player has been suspended pending an internal investigation."
Former France international Dabo, 30, signed a three-year deal with City last year.
Midfielder Barton, 24, won his first England cap in the friendly against Spain at Old Trafford in February.
Yet his early career as a first-team player at City was blighted by controversy.
In 2004, Barton was fined a club record six weeks' wages after stubbing out a cigar in team-mate Jamie Tandy's eye during City's Christmas party.
Barton ended up in more trouble during City's pre-season tour of Thailand in 2005, when he physically attacked a schoolboy Everton fan and had to be restrained by team-mate Richard Dunne.
Barton was subsequently sent home in disgrace and fined eight weeks' wages.