Chelsea expect Michael Essien to be sidelined for between four and six weeks due to the knee injury he sustained at the African Nations Cup with Ghana.
Essien was forced to return home early from the tournament in Angola after tearing his meniscus during a training session at the weekend.
The midfielder was assessed at Chelsea's Cobham training facility upon his return and manager Carlo Ancelotti has announced that the problem could keep Essien out of action until March.
However, with Chelsea winning their past three games and scoring 14 goals in the process, Ancelotti is unlikely to go back on his vow not to enter the transfer market in what remains of January.
''He had a tear in the meniscus, and he has to stay out for four to six weeks," Ancelotti said. "I hope four. In January, Essien was not here. He was at the African Cup. Maybe we lose him for one month. It is not good news but I think that we will do a good job again."
Ancelotti also insists Joe Cole will be a Chelsea player next season even though he cannot guarantee him regular first-team football. The Italian coach will leave Cole on the bench for Saturday's FA Cup fourth-round tie against Preston at Deepdale.
The England midfielder's current contract at Stamford Bridge expires in the summer and talks over a new deal have yet to reach a conclusion. The main stumbling block is understood to be Cole's desire for regular first-team football as opposed to a massive hike in his salary.
But while Ancelotti insists the player will still be at the club next season, like the rest of his squad, he cannot guarantee the 28-year-old a regular place in the starting line-up.
"No, I cannot guarantee to Joe Cole that he'll play for Chelsea in every game,'' said Ancelotti. "I cannot guarantee that to any of my players. I never guarantee that to my players, even the big players. How can a manager guarantee that to the players? That's impossible.
"I don't have any news on his contract. He will stay at Chelsea next year. I'm 100% clear. I don't like to speak about him all the time. He will be in the squad for next year, as I say.
"It's my aim. It's the aim of the club to keep him in the squad because Joe Cole is an important player, a very professional player, he has a lot of quality and is young. He is a player of the national team. He is English. For these reasons, we want to keep him in the squad."