Chelsea are refusing to speculate on the extent of the knee injury which has ended Michael Essien's Africa Cup of Nations campaign.
The Ghana ace was hospitalised in Angola over the weekend after he picked up a training ground injury which is serious enough to end his participation in the three-week tournament.
Several reports have suggested the 27-year-old midfielder could miss the rest of the season with serious ligament damage.
Meanwhile, other suggestions are that he will be sidelined for four weeks with a more minor problem and would only miss key games against Arsenal in the Premier League and Internazionale in the Champions League.
However, Chelsea are refusing to discuss Essien's injury situation until he returns to their Cobham training base later in the week for a full assessment.
"We are aware of the injury to Michael and have been in contact with the Ghanaian national team," said a club spokesperson.
"We will fully assess the injury on Michael's return to us later this week. Until then we are unable to comment further."