The 30-year-old Idrissou, who has won 34 caps for Cameroon, came off after an hour of his team's 2-1 defeat to Wolfsburg on Friday night and club doctors report he has an abcess on his throat which may require an operation.

Having scored four goals in 23 games this season, Idrissou is doubtful for next Saturday's German league clash with Hoffenheim.