Hamburg's Dutch defender Joris Mathijsen will be out for about eight weeks with torn ligaments in his right ankle.
The Bundesliga club says doctors still have to determine whether Mathijsen needs surgery.
Mathijsen was hurt when he landed awkwardly during the Netherlands' 1-0 win over Turkey in a friendly on Wednesday.
He joins a long list of Hamburg injuries. Ivory Coast defender Guy Demel also returned from national team duty with an Achilles' tendon injury. Hamburg will be missing 10 players for Saturday's match against Hannover.