Chelsea have confirmed Michael Essien is out of the African Nations Cup with a knee injury.
Ghana's team doctor has already claimed Essien, 27, will be out of action for at least a month after suffering the injury in training. Scans on Essien's left leg in Luanda are understood to have shown that he has suffered a partially torn medial collateral ligament in his knee and damage to his meniscus.
"We are aware of the injury to Michael and have been in contact with the Ghanaian national team," said a Chelsea spokesman.
"We will fully assess the injury on Michael's return to us later this week. Until then we are unable to comment further."
Essien's injury is a massive blow to both Ghana and the Blues. Ghana were hoping he would recover from the injury to play some part in their vital Group B clash with Burkina Faso on Tuesday.
But if his injury is as bad as first feared, then Essien is likely to miss Chelsea's Premier League encounter with Arsenal at Stamford Bridge and the opening leg of their Champions League tie against Jose Mourinho's Inter Milan.
Ghana's players feared the worst when Essien, who has only just recovered from a hamstring problem, went down during a training session.
"This is a big blow because Michael is so important to our team," said striker Matthew Amoah.
"We've lost the motor in our midfield, and this is very bad."
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