David Moyes says he is gutted for Paddy McNair who is facing spending the rest of the season on the sidelines..
The club today confirmed the midfielder ruptured his cruciate ligament in the 3-0 win against Hull City on Saturday.
No definite timescale has been put on his absence but such an injury would almost certainly rule him out for the remainder of the campaign as Moyes explained.
“We won’t see him again this season and all we can hope is getting him right for the start of next season," the manager told www.safc.com.
McNair was injured just before the break at the Stadium of Light and looked in some pain.
But after lengthy treatment he continued and played his part in the Black Cats' first home Premier League victory of the season, a result which moved the club off the bottom of the table.
However, McNair was hurt again late on and was substututed, with his former Manchester United pal Donald Love coming on in the dying minutes.
It represents another major blow to boss David Moyes and Sunderland, with skipper Lee Cattermole out for four months after hip surgery, and Jan Kirchhoff and Seb Larsson just on the comeback trail.
And it is a serious set-back for the 21-year-old who has made nine Premier League appearances for the Wearsiders following his summer move from Old Trafford.
The Northern Ireland midfielder, who represented his country at Euro 2016, had played in the middle in the club's back-to-back wins against Bournemouth and Hull.
To add further frustration to McNair, his op will not take place until next month.
“He probably won’t have his operation for over a week because he’s got a cut on his knee and they can’t operate while there is an open wound," said Myees. "So we have to wait until that heals so it might be a week or two."