Bayern Munich's Ribéry limps off with suspected knee injury
The 34-year old Frenchman was helped off in the 61st minute in the game against Hertha Berlín, another disappointment in this early part of the season.
More pain for Bayern
The 34-year-old Ribery, who is out of contract next June, was in clear distress after sprinting for the ball in the 62nd minute and had to be helped off.
Sagnol is in temporary charge after Carlo Ancelotti was sacked on Thursday after Bayern's 3-0 drubbing at Paris Saint-Germain.
Bayern went 2-0 up at Berlin's Olympic Stadium with goals by Mats Hummels and Robert Lewandowski before Hertha roared back with goals by Ondrej Duda and Salomon Kalou.
The result left Bayern second in Germany's top flight, but five points from Bundesliga leaders Borussia Dortmund.