Ghana have been hit by a severe blow with confirmation that captain Michael Essien will be ruled out for the rest of the African Cup of Nations with a knee injury. The Chelsea midfielder suffered an interstitial tear in the media ligament and Ghana's medical staff believes he will be out for at least one month. Essien has just returned from a hamstring tear in Ghana's 3-1 defeat to Ivory Coast last week when he was brought on at half-time. The Black Stars must beat Burkina Faso in the final Group B game on Tuesday in order to join the Ivorians to the last eight.