John O'Shea could be a doubt for Republic of Ireland's Euro 2012 campaign, according to Sunderland boss Martin O'Neill.

The defender aggravated a calf injury in the Black Cats' 1-0 defeat to Manchester United at the Stadium of Light on Sunday. His manager O'Neill has admitted that the 31-year-old could now miss this summer's tournament.

"John didn't feel comfortable. He has come back and he was starting to feel his injury, so he just didn't feel confident at all about moving on it," said O'Neill.

Asked if that could ruin his chances of playing at Euro 2012, O'Neill added: "It might do. As he came off, that was my thought, that there might be a concern about it.

"I haven't had a chance to check with the physios since that. Maybe I am jumping the gun, but it might be a concern."

Sunderland finished the season in 13th place.