Chelsea captain John Terry is doubtful for the club's busy holiday schedule after being ruled out of the Premier League trip to Aston Villa on Sunday.
Terry injured his knee against Liverpool last month in his first game back after serving a four-game ban and is still to feature under new manager Rafa Benitez.
The injury, which also ruled Terry out of the World Club Cup in Japan last week, is proving more complicated than first thought, Benitez told a news conference on Friday.
"The knee is quite complicated," Benitez said. "At least he's now on the pitch - that is positive news - but we cannot say, we cannot predict how long it will take."
"I hope so but I am not a doctor," added the Spaniard when asked whether Terry might return to face Norwich City on Boxing Day. "I cannot guarantee anything."