Bayern defender Lucas Hernandez suffered an injury during his side's game against Werder Bremen, putting him in doubt for the RB Salzburg match.
The French player was taken off after 18 minutes of the Bundesliga match following a fall.
"Lucas crashed on the ground with full force on his pelvis and had problems stepping. We have to wait and see how it develops," Bayern coach Hansi Flick told a news conference.
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The Bavarians host Salzburg on Wednesday in their Group A game, with the German title holders in first place with three wins from three matches so far.
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