"Coman will be out for two months," Bayern said in a statement on Friday after the 20-year-old suffered a torn capsule in his left ankle and torn ligaments in his knee.
He was injured while preparing for France's World Cup qualifier against Sweden on Friday.
There was some good news, though, for Bundesliga leaders Bayern who are chasing a record-extending fifth consecutive title.
Spain defender Javi Martinez has made a quicker recovery than expected and is set to return to training next week following the adductor muscle injury he sustained early last month.
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"It is even possible he will be at the disposal of coach Carlo Ancelotti for the match at (Borussia) Dortmund on Nov. 19," Bayern said.
The Bavarians lead the Bundesliga on goal difference from promoted RB Leipzig after 10 games.
Bayern have also secured a spot in the Champions League knockout stage with two group matches to spare.
(Reporting by Karolos Grohmann; Editing by Tony Jimenez)
