Arsenal midfielder Mesut Ozil missed Germany training on Friday after suffering a back injury.
The former Real Madrid star sat out the Gunners's final Premier League match before the international break with a hamstring problem that also ruled him out of Wednesday's friendly win over England.
And Ozil has now picked up another injury that could yet see him miss Die Mannschaft's World Cup qualifier against Azerbaijan on Sunday.
The 28-year-old has travelled with the rest of the squad to Baku, though Borussia Dortmund midfielder Julian Weigl has returned to his club.
Weigl picked up a thigh injury in the win over England and was replaced in the second half by Emre Can.