Striker Didier Drogba needs minor surgery on the groin injury that forced him to limp off during Chelsea's 1-0 home win over Liverpool on Sunday.
The 26-year-old had already been withdrawn from the Ivory Coast's World Cup qualifier against Benin on Sunday.
But the operation is expected to rule the forward out for five weeks.
Chelsea boss Jose Mourinho told the club's website: "He has an injury that the medical department has found best to solve with a little surgery."
Mourinho added: "We think in four
or five weeks he can be back."
Drogba has netted five times for the Stamford Bridge outfit since joining the Londoners from Olympique Marseille for
£24m in July.
But his injury means his club must definitely do without him for the forthcoming Premiership match against Manchester City and the home Champions League encounter with CSKA Moscow.
He is also likely to miss league games against Blackburn and West Brom later in the month, plus the Carling Cup third-round date with West Ham.