Sunderland have been left rocked by the news that Jan Kirchhoff has been left facing a fight to play again this season.
The German made his return for the U23's against Manchester United but his knee suffered from swelling immediately after the game. Kirchhoff completed 60 minutes in that match.
David Moyes has now said that the German faces a minimum of four weeks on the sidelines as he deals with the latest injury blow to rock the club.
Kirchhoff had been expected to make his first team return in a key game against Burnley on Saturday.
Moyes is confident that his knee will heal, but perhaps not in time to make a significant contribution to Sunderland's relegation fight.
Moyes said: "Jan has unfortunately had a reccurence of his knee problem and it looks like it is going to keep him out for a minimum of four weeks.
"He came back and played in the reserves against Manchester United about two weeks ago, his knee swelled up immediatley after the game.
"He only trained for a couple of days and then pulled out. He has been back to see the surgeon and I don't think there is any damage, but it is going to take longer than we thought to heal.
"He had some [injury] problems before he came, he had some periods that he missed out. I genuinely think his knee will heal up, it will just take a little more time – and we are running out of time.
"We had arranged a behind-closed-doors game for him this week, we also had a reserve game last Sunday that he couldn't play in.
"We haven't been able to use him since he played 60mins in that game [against Man U].
"He has been told at the moment that it will be at least another four weeks.
"I don't know where that takes us to, but it might be too close to the end of the season.
"We might be able to use him in one or two games, but we will have to see."