Controversy-prone Manly winger John Hopoate faces disciplinary action from his National Rugby League club after admitting he secretly played in a fifth-grade rugby union match.

Hopoate caused a stir when he went on as a replacement and scored the match-winning try for Parramatta in its 19-17 club rugby win over West Harbour on Monday.

He initially denied playing the rugby union game but admitted to Manly officials that he had done so, following publicity about the incident.

West Harbour players recognised Hopoate on the field and questioned how he could be allowed to play while Manly officials were concerned that he'd breached his contract terms.

Manly chief executive Ian Thomson said Hopoate had been "sadly misguided" in deciding to play.

"How did he ever think he would get away with it?" Thomson said.

"I mean, he's probably known the world over, let alone in the Sydney metro area.

"Knowing John as I do, it wouldn't have been pre-meditated - his brothers and cousins were playing and he probably had to borrow a pair of boots to get on there.

"But that doesn't excuse it - I'll get all the facts and we'll take the appropriate action, probably by Friday."

Hopoate, 29, has had a chequered rugby league playing career.

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