Corentin Tolisso will spend several months on the sidelines after tearing his anterior cruciate knee ligament in Bayern Munich's win over Bayer Leverkusen on Saturday.
The Bundesliga champions also confirmed full-back Rafinha is set to miss "a number of weeks" with ankle ligament damage sustained during a bruising encounter at Allianz Arena.
Rafinha's injury came as the result of a lunging Karim Bellarabi challenge which earned the winger a red card and was branded "sick and stupid" by Bayern president Uli Hoeness.
World Cup winner Tolisso, who cancelled out Wendell's early opener, went down in the first half and presents the greater concern for Niko Kovac.
The midfielder is set to miss a large chunk of the season, potentially forcing the new Bayern boss to dip into the transfer market in January.
The club's Champions League campaign begins away to Benfica on Wednesday and winger Arjen Robben admitted it was an unfortunate time for depth to be tested.
"[Tolisso] is a good player and we've said that many times," Robben told reporters after the match.
"We need all the players, especially in such a phase. That's very bitter, especially for himself."
Robben and James Rodriguez added to Tolisso's equaliser with goals either side of half-time to maintain Bayern's perfect record after three matches.
