Chelsea keeper Petr Cech will have a scan on a leg injury after being forced off at half-time during the 2-1 victory over Everton on Sunday.
Cech failed to return for the second half and was replaced by Ross Turnbull after straining an adductor muscle at the top of his leg at Goodison Park.
He was initially thought to have hurt his ankle but interim manager Rafael Benitez clarified the problem and revealed the keeper could miss Chelsea's clash against west London rivals Queens Park Rangers on January 2.
"He felt something in his adductor and we didn't want to take the risk," Benitez said. "We will have to do a scan and see what it says."
Benitez also said the game will come too soon for captain John Terry, who is recovering from a knee injury.
"We have to recover quickly and be ready," Benitez said. "QPR are in a difficult position and that means they will be more dangerous so we have to be focused on what we have to do and try to improve the things that we are not doing well.
"Still we are making some mistakes which we have to manage but the team is much better and the main thing for me is the attitude of the players. They are keen to learn and we are really pleased with the way they train and behave every day, and that is the main thing for the future."