The Africa Cup of Nations left Carlo Ancelotti 's Chelsea without midfielders Essien and Mikel .
Later in the season the Africa Cup of Nations left Chelsea without strikers Solomon Kalou or Didier Drogba ( as well as midfielders Essien and Mikel ) and harder to play 4-4-2 , so Ancelotti switched to the 4-3-2-1 `` Christmas Tree '' formation he had used at Milan , using Joe Cole and Florent Malouda to support lone striker Nicolas Anelka .
Carlo Ancelotti