Sunderland midfielder Jan Kirchhoff will miss "a minimum of six weeks" after suffering a hamstring injury, the club have confirmed.
Kirchhoff, 26, was stretchered off during the Black Cats' 1-1 draw with West Bromwich Albion on Saturday.
A scan has shown the extent of the injury means the former Bayern Munich man will be sidelined for up to eight weeks.
A club statement said: "Jan Kirchhoff has been ruled out for a minimum of six weeks after suffering a hamstring injury during Sunderland's draw against West Bromwich Albion.
"The former Bayern Munich player was stretchered off in Saturday's game at the Stadium of Light and in order to assess the extent of the injury, the 26-year-old underwent a scan which revealed he will be out for six to eight weeks.
"The midfielder will now focus on returning to action as soon as possible.''
The news will come as a blow to Sunderland manager David Moyes, whose side sit bottom in the Premier League having earned just two points from their opening seven games.
Kirchhoff joins Adnan Januzaj in being unavailable, the Manchester United loanee suffered ankle ligament damage during the 3-2 defeat against Crystal Palace and will be out for a similar amount of time.
Lee Cattermole, Steven Pienaar and Victor Anichebe also unavailable at the weekend. In addition, keeper Vito Mannone, midfielder Sebastian Larsson and striker Fabio Borini are all long-term absentees from a squad which is looking thinner by the week.