Police have interviewed Parramatta star Jarryd Hayne and another man following an alleged assault at a Kings Cross nightclub in the early hours on Sunday morning.

Appealing for witnesses to the alleged incident, police confirmed they had spoken to a 23-year-old and 25-year-old about the allegation.

"About 1.20am today (Sunday), two men aged 23 and 25 were at a nightclub in Roslyn Street," a police statement said.

"Police are investigating allegations that the men became involved in an altercation, which resulted in the 25-year-old sustaining a cut about his eye.

"He was taken to St Vincent's Hospital, however he left before receiving treatment.

"Both men have been interviewed by police and investigations are underway into the circumstances surrounding the alleged incident."

The Eels are sticking by Hayne, 23, following a second incident in the notorious Sydney suburb in three years.

The NRL club says the NSW State of Origin back retaliated to an assault, reportedly a headbutt, and made a complaint to police.

It is believed Hayne was out celebrating a friend's birthday, but the incident comes after Hayne was shot at in Kings Cross in 2008 following an altercation in another nightclub.

The Eels released a statement on Sunday saying the club had assisted their five-eighth in reporting the incident.

"The Parramatta Eels have this morning filed a complaint with police regarding an incident involving Jarryd Hayne last night at Beach Haus nightclub," the Eels statement read.

"Hayne has told investigators he was confronted by a patron and assaulted before retaliating in self-defence.

"Eels chief executive Paul Osborne accompanied Hayne to Parramatta Police Station this morning to report the assault and lodge a formal complaint.

"The Eels will await further contact from the police regarding their investigation of the incident before making any further comment."

Osborne also told The Daily Telegraph: "At this stage we believe he did nothing wrong."

In March 2008, a man reportedly involved in a fight with several NRL players inside the Sapphire Suite nightclub fired shots from the back seat of a taxi at Hayne at around 4am in the morning.

At the time, NRL boss David Gallop described the incident as a "bloody ugly headline for the game" but said blanket curfews for players were not the solution.

That incident was considered one of the factors in Hayne embracing Christianity after also spending time with the religious Fiji World Cup team.

The incident comes at a sensitive time, as the NRL's incoming commission prepares to ramp up negotiations with broadcasters, hoped to fetch up to $1.4 billion for the game.

The NRL has this year avoided the litany of unsavoury off-field problems that plagued the code in recent years, but has dealt with high profile incidents involving Dally M medallist Todd Carney and Benji Marshall.

Carney was found guilty of a third drink driving offence in April and stood down for several weeks by the Sydney Roosters.

Marshall faces court in August over a charge of assaulting a man at a McDonald's restaurant in the Sydney CBD.

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