Schalke striker Soren Larsen has been ruled out for six weeks with a knee injury.
The Danish international, who moved to the Arena AufSchalke from Brondby last summer, scored a crucial late winner in the 1-0 Uefa Cup victory over Nancy on September 14.
The Royal Blues have made a good start to the new season, but he picked up a partial ligament tear to his left knee in the 2-0 defeat to league leaders Hertha Berlin on Sunday.
Club doctors insist the 25-year-old does not require surgery, but he is set to be out until the end of October.
Team-mates Hamit Altintop and Zlatan Bajramovic are meanwhile doubtful for the Royal Blues' game against Wolfsburg on Saturday because of bronchial problems.