MIAMI -- Mark Philippoussis, forced to retire from his first round match at the U.S. Open, is expected to miss two months because of a hyper-extended left knee and bone bruise.

Philippoussis underwent an MRI on Wednesday and although there is significant swelling and pain, Dr. Harlan Selesnik said surgery would not be necessary.

"I'm obviously upset at having the injury and that I will have to miss the Davis Cup tie in Adelaide and the upcoming tour events,'' Philippoussis said. "I'm delighted that the injury is not as severe as I first thought and I will be able to continue to show improvement and get better in the future.''

Philippoussis has had three operations on his left knee since 1999 but Tuesday's injury, which occurred in the fourth set against Sjeng Schalken, was not related to the previous injuries.