Chelsea midfielder Michael Essien is expected to be sidelined until January after undergoing knee surgery on Monday.
The Ghana international, who has a history of knee injuries, ruptured the anterior cruciate ligament and the meniscus in his right knee in pre-season training last week.
The injury is said to have stunned Chelsea officials, who were expecting scans to reveal a simple twisted knee after Essien fell innocuously during a training drill.
Instead, the 28-year-old has had surgery to repair the torn structures and faces up to six months of rehabilitation before he can return to the Blues.
It is Essien s third serious knee injury in three years. The midfielder missed a large chunk of the 2008/09 campaign due to cruciate ligament damage and was forced out of the 2010 World Cup with a less severe medial ligament injury.
New Chelsea boss Andre Villas-Boas said: Everyone at Chelsea wishes Michael well for his recovery.
His team-mates and all the staff and I look forward to helping him return to playing as soon as possible.
