The German soccer federation said Monday that the 23-year-old Koch, who played at the Under-21 European Championship in June, has been called up for the first time. Rudy returns for the first time since November last year.
Both Timo Werner and Ilkay Gündogan are doubtful for Wednesday's friendly against Argentina in Dortmund. Werner has a cold and Gündogan a "minor muscular injury," Löw said. Real Madrid midfielder Toni Kroos and Cologne defender Jonas Hector dropped out on Sunday, adding to Germany's injury list of Antonio Rüdiger (Chelsea), Leon Goretzka (Bayern Munich), Kevin Trapp (Eintracht Frankfurt), Nico Schulz (Borussia Dortmund), Leroy Sané (Manchester City) and Paris Saint-Germain pair Julian Draxler and Thilo Kehrer.
Schalke midfielder Suat Serdar and Bayer Leverkusen's Nadiem Amiri was called up on Sunday for the first time, meaning five players could make their debuts on Wednesday. That also includes Freiburg forward Luca Waldschmidt and Hertha Berlin defender Niklas Stark.
Germany plays Estonia in a Tallinn in a qualifying game four days later.
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