Sport Football Chelsea [h=1]Michael Essien's Chelsea woes go on after injury in pre-season training[/h] Ghanaian a doubt for pre-season tour to Asia Midfielder suffered anterior cruciate injury in September 2008 Share9 reddit this Jamie Jackson guardian.co.uk, Friday 8 July 2011 16.43 BST Article history Michael Essien has suffered an injury during pre-season training with Chelsea. Photograph: Tom Jenkins for the Guardian Michael Essien is undergoing tests after suffering an injury during pre-season training with Chelsea. It is not yet know what the problem is, and how serious the injury may be, with a clear prognosis not due until sometime over the weekend. There has been no confirmation or denial from the club of speculation on Twitter that the midfielder may have suffered a cruciate injury. "Michael Essien suffered an injury to his right knee during training this week," Chelsea said. "He will undergo tests over the next few days to determine the extent of that injury. Until we have the full results of those tests we will not be commenting further." André Villas-Boas, the new manager, must fear he will be without the influential Ghanaian for the club's pre-season tour to Asia which starts in a fortnight. Essien suffered an anterior cruciate injury in September 2008 that ruled him out until the following March.