Chelsea face an anxious wait to discover the full extent of the hamstring injury which has ruled Michael Essien out of Saturday's Premier League clash with Everton at Stamford Bridge. The all-action midfielder scored an equaliser for the west London club against APOEL in his side's final Champions League game on Tuesday, which ended 2-2, but then broke down in the centre circle in clear discomfort. The Premier League leaders will make a full assessment on Wednesday but fear the Ghana international may have suffered a torn hamstring, which could sideline him for six weeks and put his African Nations Cup availability in doubt. "Michael has a problem with his leg," said manager Carlo Ancelotti. "We will look at him over the next few days and check on him. "We hope it's not a big problem but he will not be able to play on Saturday."