Chelsea could be without influential midfielder Michael Essien until February after scans proved that the Ghanaian will be out for four weeks before the African Cup of Nations. Essien sustained a torn hamstring during Chelsea's 2-2 Champions League draw with APOEL Nicosia on Tuesday, following his magnificent strike for the Blues. Come the time of his return, the tenacious midfielder will be joining Ghana for the Angola finals on January 10th, which means he is likely to miss more club action. Chelsea will face a genuine challenge when the African showdown kicks off, with Essien and Didier Drogba expected to leave a huge gap in Carlo Ancelotti's roster.