Mark Hughes is assessing the fitness of Luke Young and Bobby Zamora after Queens Park Rangers' 2-1 defeat by Wolves.
Both players were substituted during the game at Loftus Road on Saturday.
Young has made 21 league appearances since moving to QPR last August and will be assessed over the next 48 hours but is a major doubt for the clash with Blackburn.
Hughes said: "He felt his hamstring. Hopefully it's not too serious but it does look like he'll now be missing."
Zamora was making his debut for the London club and Hughes says the decision to withdraw the striker was a precaution after he had earlier put his new club in front.
He added: "Bobby was cramping up. He should be okay.
"He didn't want to damage himself any further and was correct to say 'I want to come off'. It was to protect him."