Park Ji-sung's agent has confirmed the player has flown to America to undergo tests on his knee injury.
The Manchester United has been struggling with a knee complaint since the game with Blackburn at the end of March.
It is feared the South Korean international has suffered a serious knee injury which could sideline him for several months.
United have decided to send Park to America to have consultation on his knee injury as they look to resolve the problem.
The player's representative Chiel Dekker confirmed Park had travelled to America for tests on the injury and admitted the player was disappointed to suffer the injury at such a crucial stage of the season as United look to maintain their bid for the treble.
"Park has flown to America to have tests on his knee injury," Dekker told skysports.com.
"My Korean business partner has flown with him to find out what the problem is
"It seems to be serious and it looks like he will miss the rest of the season.
"He is disappointed to be out injured and it has come as something of a shock to him as he didn't think it was serious when he first sustained the injury against Blackburn.
"We are now waiting to find out the full extent of the injury."
United boss Sir Alex Ferguson confirmed Park would miss the rest of the season with the injury."We have not been able to get to the bottom of it, so we have sent him to the best specialist in the world," said Ferguson. "Unfortunately, it puts and end to his season."