Werder Bremen says defender Leon Balogun injured his knee in a training collision with teammate Tom Trybull on Thursday.

Coach Thomas Schaaf said they were yet to determine how serious the injury was; ''we have to wait for the diagnosis.''

Saturday's league game at Hoffenheim is still too early for Brazilian defender Naldo to make his comeback after 15 months out.

Schaaf said, ''I can understand Naldo would rather play today than tomorrow, but we must proceed sensibly.''

Lukas Schmitz and Wesley were available for Werder after getting over minor knocks.