Kirchhoff was forced off early in the second half of Saturday’s 1-1 Premier League draw with West Brom at the Stadium of Light.
Manager David Moyes admitted afterwards that he was concerned the problem could be long-lasting, and the club have now announced that they do not expect the former Bayern Munich man to return until late November.
“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,” a statement posted via the club’s official website read.
“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 comes as a huge blow to Moyes, who has already lost Lee Cattermole (back), Steven Pienaar (hamstring), Adnan Januzaj (ankle) and Seb Larsson (knee) to injuries.