London - Chelsea and Ghana midfielder Michael Essien will be out of action for up to six weeks after returning from the African Nations Cup with a knee injury, his club announced on Friday.
Essien, 27, damaged cartilage while training in Angola and although the injury has not proved as serious as first feared, he is unlikely to return before early March.
"He had a tear in the meniscus, and he has to stay out for four to six weeks," Chelsea manager Carlo Ancelotti revealed. "I hope four."
The lay-off means Essien will miss Chelsea's potentially pivotal Premier League meeting with Arsenal and the first leg of the club's Champions League second round tie against Inter Milan in Italy.
An ankle problem has meanwhile ruled Ashley Cole out of Chelsea's FA Cup fourth round tie at Preston on Saturday.
Yury Zhirkov will deputise while Hilario will get a rare start in goal with Petr Cech rested for the meeting with opponents struggling in the bottom half of the Championship.