Didier Drogba could require a knee operation that would rule him out of action for at least a month.

The Chelsea striker is believed to have had a scan yesterday that revealed a problem in his left meniscus, which requires surgery.

But with Drogba due to leave Stamford Bridge next month for African Nations Cup duty with Ivory Coast, it remains to be seen whether Chelsea will opt to place their striker under the knife immediately or ask him to struggle on during the critical Christmas period.

Reports in England suggest Chelsea's medical staff will examine Drogba's training performance today before advising manager Avram Grant of the best course of action.

If Drogba is deemed unfit to face Sunderland on Saturday it is thought they are likely to recommend an operation as soon as possible.

The situation is further complicated by Drogba's understandable reluctance to risk his long-term health as well as his desire to represent his country.

An operation would rule the Ivorian out of action for a minimum of five weeks, meaning it is distinctly conceivable that Drogba will not play again for Chelsea until February.