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.
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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.