Jacques Santini revealed that Sean and fellow midfielders Michael Brown and Michael Carrick had picked up knee injuries.
However, while Sean is definitely out, both Michaels are in the initial 18-man list and Jacques will make a late decision on their fitness.
"Sean, Michael Brown and Michael Carrick all have knee problems," said Jacques. "Sean has had the problem for about eight days and two or three days ago, after training, he went to see the doctor. So he is not available for this game.
"I will wait until our last training session on Saturday for the information on Michael Brown and Michael Carrick.
"It is good news for Simon and the team that he is ready to play."
Simon Davies is back in the squad for Sunday's clash against Norwich City at the Lane - but Sean Davis is out.