St Helens centre Mark Percival faces up to three months out after he ruptured medial ligaments in his knee.
The 21-year-old suffered the injury at the AJ Bell Stadium as Saints lost 44-10 at Salford Red Devils on Thursday.
Percival scored two tries as Saints won their Super League opener against Huddersfield six days earlier.
"Luckily we've got plenty of players and a bit of thickness in our squad," head coach Keiron Cunningham told BBC Radio Merseyside.
After their defeat at Salford, Cunningham's side host Australian side Sydney Roosters in the World Club Series opener on Friday.
"We're all excited about the game, we got rid of the hangover from the weekend," he added.
"It wasn't a pretty video, it was a bit raw but sometimes you've just got to rip the plaster off and move on and that's what we did.
"I'm really hopeful we'll be a better side on Friday."