O’Shea has suffered complications to a leg injury he suffered while away on international duty for the Republic of Ireland two months ago.
United boss Sir Alex Ferguson said: “He’s got a terrible injury at the moment.
“The problem is that the blood clot became all knotted and when it gets knotted you get calcification, so therefore it’s a long process.”
“He’s probably out for the season now,” added the United boss. “It’s a bad blow for the boy and for the team because he can play anywhere.”
