Chelsea look set to be without Michael Essien for the rest of the year after it was confirmed the midfielder would need surgery on a knee injury.
The 25-year-old suffered the problem while on international duty with Ghana.
A club statement read: "Michael has ruptured his anterior cruciate ligament and will undergo an operation as soon as the majority of the swelling has subsided. We expect this to happen in a week's time.
"In the meantime, Michael has started rehab in the aqua therapy centre at Cobham which will improve the condition of the knee prior to surgery. A return to full fitness is not expected for several months."
The loss of the combative Ghanaian for such a long period is a major blow to the Blues, who have no like-for-like replacement available and will not be able to buy any fresh faces before the transfer window re-opens in January.
Essien had landed awkwardly during the World Cup qualifier against Libya, and was immediately taken to hospital for scans, with the diagnosis now confirmed by Chelsea's own medical staff.
Luiz Felipe Scolari's men - who opened the new campaign with two wins and a draw - are next in Barclays Premier League action away to Manchester City on Saturday before then embarking on their European campaign at home to Bordeaux and a clash with champions Manchester United on September 21.