The Daily Mail has reported that the player, who cannot be named for legal reasons, was held on Sunday following the report of an attack at a nightclub the day before.
The paper reported that a 41-year-old woman was also held on suspicion of administering a substance with intent to cause a sexual offence.
Both have been released on bail while investigations continue.
A police spokesperson, quoted in the newspaper, said: “Officers were called shortly before 11am on Sunday January 9 to a report of a sexual assault on a female.
“A woman in her late teens was reported to have been sexually assaulted.
“Both have since been released on bail as enquiries continue and a number of lines of enquiry are being followed up by detectives.”
The Rugby Football Union has refused to comment.