Summary:
Chelsea midfielder Michael Essien will be out for up to six months after having surgery on his knee.

Full article:
(CNN) -- Chelsea midfielder Michael Essien will be out of action until 2012 after undergoing surgery on his right knee. The 28-year-old Ghana international damaged ligaments in his right knee during training last week, the third serious knee injury of his professional career. The English Premier League side confirmed the news in a statement on their official website. Villas-Boas confirmed as new Chelsea manager . "Following an injury to his right knee in training last week, Michael Essien has had surgery to repair a ruptured anterior cruciate ligament and meniscus." The statement continued: "The surgery was successful and Michael's full recovery could take up to six months." Meanwhile, New Chelsea manager Andre Villas-Boas added: "Everyone at Chelsea wishes Michael well for his recovery. "His teammates and all the staff and I look forward to helping him return to playing as soon as possible." Essien's injury could see Chelsea enter the transfer market for a replacement, with Tottenham's Luka Modric and Porto's Joao Moutinho both being heavily linked with a move to Stamford Bridge.