Manchester United have sent Park Ji-Sung to the United States for knee surgery to be carried out by the specialist who saved the careers of Alan Shearer and Michael Owen. Park is one of a number of Sir Alex Ferguson's squad who have been forced on to the sidelines as the club's treble bid reaches its climax.

But while the manager is optimistic about an imminent return of Louis Saha, Nemaja Vidic and Rio Ferdinand, he concedes the Korean winger's injury will rule out any chance of a return this season. Park suffered the knee injury in the final minute of United's victory over Blackburn Rovers on 1 April, and the club has now been forced to enlist the help of world renowned surgeon Dr Richard Steadman in a bid to diagnose the full extent of the problem.

Ferguson hopes that Park's transatlantic visit will increase the possibility of the player making an early return at the start of next season. "There's no improvement in his knee injury and we've sent him to see some other specialists but we now just have to get him to the best," Ferguson said.

"There was an option to send him to Sweden or America and we decided to send him to the States to see Richard Steadman in Colorado. There was no clear reason for the injury and we couldn't get to the bottom of it. So we decided we should send him to the best in the world."