Rafael Benitez cannot guarantee John Terry will be fit for Chelsea's Christmas fixtures.
Terry's recovery from knee surgery is proving more problematic than first thought and he will definitely miss Sunday's Barclays Premier League game against Aston Villa.
Ramires and Gary Cahill return from suspension but John Obi Mikel is still banned. Daniel Sturridge is available for selection after his hamstring injury but Ryan Bertrand is doubtful after being forced off in Wednesday's Capital One Cup quarter-final at Leeds.
Benitez has claimed Fernando Torres's long-awaited return to form is proof that his Chelsea revolution is working.
Almost two years since Torres' record-breaking move from Liverpool and he is finally starting to score the number of goals to justify his £50million price tag.
Six in five games is by far the most sustained run of the 28-year-old's Stamford Bridge career and it has co-incided almost exactly with his reunion with former Anfield boss Benitez.
Chelsea's interim manager immediately identified that Torres had lost some of the physical conditioning that had made him one of the most feared forwards in the world, as well as an obvious lack of confidence from failing to find the back of the net.
``Two or three things that we are doing for some players are really good,'' Benitez said, claiming the sharpness in the majority of his players was now ``much better''.
``Fernando is one of the examples.''
He added: ``He's scoring goals and the team is winning and playing well, so he's really happy, not just because he's scoring goals but also because the team's doing well.''
Despite the clear impact Benitez has made on Torres, he played down the extent of his own influence on his fellow Spaniard.
``I think that the team has an influence on him because the team is doing well, so the team is playing better, creating more chances,'' he said.
``So Fernando is taking more chances.''
Villa midfielder Stephen Ireland is available after missing the 3-1 win over Liverpool at Anfield last weekend through illness.
But skipper and central defender Ron Vlaar and striker Gabriel Agbonlahor remain major doubts with calf and thigh problems respectively.
Villa are unbeaten in their last five league games and also reached the semi-finals of the Capital One Cup.
But boss Paul Lambert still expects Chelsea to pose a formidable threat despite their hectic schedule and travelling back from the World Club Championship in Japan.
He also has immense respect for Benitez.
Lambert said: ``I hope the travelling affects them - but I don't think it will. They had a good result the other night against Leeds.
``The tiredness only comes in if you are not getting results, if you're winning nobody bothers.
``In terms of Rafa, you look at his managerial career and it is phenomenal.
``He's gone in there at a difficult time and tried to stabilise it and get results at the same time.''