Park Sung-Jong told reporters the US surgeon who performed the operation believed his son's career could have been over had the problem not been attended to.

Park senior was speaking to local media after returning from a hospital in Colorado, where Ji-Sung had the operation on April 28. He was operated on by knee specialist Richard Steadman, who helped save the careers of Alan Shearer and Michael Owen.

Manchester United, which won the Premier League championship Sunday, has said Park had a complicated cartilage operation and would be out for the rest of the season, adding that the club would assess his condition in August.

"The operation was timely and it prevented aggravation," Park's father said. "He will have to be on crutches until August."

Park injured his right knee in a Premier League match against Blackburn Rovers on April 1.

The absence of Park and probably of another injured Premier League player, Lee Yong-Pyo, will affect the South Korean side as it prepares for the Asian Cup championships in July.