Arsenal defender Shkodran Mustafi looks set for an extended spell on the sidelines after limping out of Germany's 5-1 World Cup qualifying win over Azerbaijan.
Mustafi was forced off after just 36 minutes in Kaiserslautern with what coach Joachim Low described as a severe muscle injury.
"I think Mustafi has a muscle tear. It looks a bit more serious." Low said. "This will probably force him to have an extended layoff."
Bayern Munich's Niklas Sule was also substituted in the 22nd minute as a precaution, with Chelsea's Antonio Rudiger coming on in his place.
Mustafi has made five appearances for Arsenal in the Premier League so far this season.
Meanwhile, Mustafi's Germany teammate Leon Goretzka said he wants to make his mark for his country at the World Cup, and his showing on the day will not have hurt his chances of inclusion in Low's squad for Russia.
Goretzka scored twice, including a brilliant backheel, with Sandro Wagner, Rudiger and Emre Can also netting.
Schalke midfielder Goretzka said: "I think we were very consistent throughout the qualifiers and we deserved to qualify with a perfect record.
"I was happy with my role in the Confederations Cup, but now I think it's time to play a big role in a big tournament like the World Cup.''
Goretzka opened the scoring with a clever backheel, but Ramil Seydaev levelled before the break.
Wagner put Germany ahead ahead before Rudiger's header was deflected in off Dan Mori and Goretzka added a fourth.
Can then capped the victory with his first Germany goal with nine minutes left when his 30-yard rocket beat Agayev.