LONDON (Reuters) - Sunderland, looking for the win that could take them off the bottom of the Premier League when they host Watford on Saturday, have suffered another injury blow with Jan Kirchhoff having suffered a cartilage tear.
He is their fifth midfielder now out of action.
Manager David Moyes revealed the injury at a news conference on Friday. "As yet there is no time frame," he said.
Kirchhoff, a Germany Under-21 international signed from Bayern Munich last January, did the damage in Wednesday's 1-0 home defeat by league leaders Chelsea.
That result kept the Wearside club bottom despite a recent run of three wins in four games. They are one point behind Hull City and Swansea City, who both face away games this weekend.
"I was pleased with the performance against Chelsea and in the end their keeper made some good saves," Moyes said.
"We are in good fettle. But we have to win our home games if we want to stay in the Premier League.
"Watford have had a project over the years, added to it and they have done a good job in building the club up.
"It will be a tight game, a close one and we need to make sure we win it."
Reporting by Steve Tongue; Editing by Toby Davis