Hull KR centre Sean Gleeson is facing being blind in one eye after being attacked outside a Wigan nightclub in the early hours of Sunday morning.
The 26-year-old, who is yet to play for the Robins this season as he recovers from a broken leg, suffered serious injury to his eye and eye socket in the attack.
Gleeson is now recovering in hospital and Det Chief Inspector Howard Millington has launched an appeal for witnesses in a bid to track down the perpetrators.
"Our main concern is that a young man has been seriously assaulted," Millington told the Hull Daily Mail. "He has been left with a serious injury which could result in the loss of his eye.
"We want to hear from anyone who saw or knows something that might be relevant to our investigation. At this time of night, there would have been people around the area who may have seen this attack or saw the men running away.
"I would also urge anyone who thinks they may know who is responsible to come forward and speak to us. Imagine if this was your son, brother, cousin, or close friend who was ill in hospital, you would want answers."
Gleeson has been injury-plagued since joining KR from Salford on a three-year ahead of the 2013 season. He has played in six of the club's 33 matches since moving clubs.
A broken leg during pre-season has seen him miss the start of the current campaign for the Robins, who are still yet to register their first win in 2014.