Chelsea have been rocked by the news that Didier Drogba is facing a knee operation that could keep him out for several months. The Ivory Coast striker had a scan yesterday that revealed degeneration in his left meniscus, which requires surgery. A decision on whether to operate immediately or patch him up in the hope of getting him through the Christmas period will be made in the next few days.

Chelsea’s medical staff will speak to the player and examine his performance in training today before advising Avram Grant, the first-team coach, of the best course of action, although if Drogba is deemed not fit enough to face Sunderland on Saturday they are likely to recommend an operation as soon as possible.

Although there is a temptation to keep Drogba going with the aid of painkilling injections until January, when he will be unavailable because of the African Cup of Nations, the 29-year-old is unwilling to sacrifice his international ambitions in such a manner and the club’s medical department do not want to risk his long-term health for the sake of a few Barclays Premier League appearances.

Drogba has been carrying the injury since he took a knock to the left knee while playing for Ivory Coast last month and a prolonged period of absence would be a huge blow for his club. Chelsea are heavily reliant on their leading scorer and failed to win any of the three matches he missed with a different knee injury in September, and they scored only one goal.

The minimum recovery period from knee surgery is between three and five weeks, not including the time necessary to regain match fitness, which would keep Drogba out until the African Cup of Nation starts in January. Although Grant should be capable of masterminding a victory over Sunderland, tougher tests await, with Chelsea facing Arsenal on December 16 before potentially awkward Christmas fixtures against Blackburn Rovers, Aston Villa, Newcastle United and Fulham. Chelsea’s failure to beat Villa and Fulham over the festive period last year effectively cost them the title.

Given Drogba’s international commitments, it is conceivable that he may not play for Chelsea until February, although there could also be repercussions for his participation in the African Cup of Nations. The club are adamant that Drogba will not be permitted to complete any of his rehabilitation with Ivory Coast, who begin the tournament against Nigeria on January 21, and that he will be allowed to travel only if and when he is deemed match fit to play for Chelsea.

Grant has complained about the scheduling of the tournament and will resist any requests from Ivory Coast, Nigeria and Ghana for early call-ups for Drogba, Salomon Kalou, John Obi Mikel and Michael Essien with concern about the standard of medical care provided by the African associations.

Drogba’s absence will increase the pressure on Grant to sign a striker, with a bid for Nicolas Anelka, the Bolton Wanderers player, expected.