Premier League player Titus Bramble "strenuously denies any wrongdoing" after being arrested on suspicion of rape, Sunderland chairman Niall Quinn said.
The defender was questioned at a Newcastle police station after he and his brother Tesfaye were held at a city centre hotel.
Quinn said in a club statement last night: "This has been a very difficult day for everyone at the football club, no one more so than Titus, who categorically refutes the allegations that have been made against him."
Quinn's statement added: "He strenuously denies any wrongdoing and will be doing everything within his power to clear his name.
"I as chairman, and the club as a whole, totally support Titus in his efforts and we all hope for a swift conclusion to this matter."
Bramble, 29, who used to play for Ipswich Town, Newcastle United and Wigan Athletic, was arrested with his brother Tesfaye, 30, who has played international football for Montserrat, a British island in the Caribbean, and is a striker for Eastern Counties League Premier Division club Leiston, in Suffolk.
They were detained after the rape of a young woman was reported to police in the early hours of Wednesday morning.
It is believed the alleged rape happened at the four-star Vermont Hotel, which has an entrance close to bars and nightclubs on Newcastle's quayside.
A Northumbria Police spokesman said: "Police received a report of a rape of a woman at a city centre hotel in Newcastle in the early hours.
"Two men, aged 29 and 30, have been arrested on suspicion of rape."
Bramble, a former England under-21 player, was signed by Sunderland manager Steve Bruce from Wigan for a fee thought to be around £1 million in the summer.
A spokesman for the Premier League player's solicitor, Mark Haslam, refused to comment, as did hotel staff.