Joe Westerman will be sidelined for up to three months after dislocating his shoulder against London.
Westerman injured his shoulder as he scored a try to help Hull FC to a 22-14 win over the Broncos.
He will undergo surgery before starting a three month rehabilitation period.
Hull FC coach Peter gentle said: “We are tremendously disappointed for Joe, as he was really starting to show signs of what we are looking for from him.
“It does mean it opens the door for another member of the squad to take the opportunity to step up and we’ll be looking to see who can do that over the coming weeks.
“We have talked about competition for places and the door is now open for someone to take their chance.”