Because Schlotterbeck isn't expected to recover from his injury before October. 
Niko Kovac should handle the situation depending on Süle's physical condition. You know he gained lots of weight earlier. Lastly, they need an immediate LW signing. Duranville is the only option (who is injured and not even knowing his return date) after selling Gittens.
Schlotterbecks injury he got is the neckbreaker here and he is missed to 100% in the deffense.Niko Kovac should handle the situation depending on Süle's physical condition. You know he gained lots of weight earlier. Lastly, they need an immediate LW signing. Duranville is the only option (who is injured and not even knowing his return date) after selling Gittens.
The situation about Niklas Süle was already when he joined Dortmund and also the last year he played for Bayern Munich.
He made a nice transformation last season with his body but with age of 29 he should be playing better as he has done last season and before.