The 19-year-old Canadian international collapsed on the pitch in the opening minutes at the Allianz Arena in noticeable pain after awkwardly planting his right leg.
"He sustained a ligament injury. One ligament is fully torn, another is partially torn. We reckon he'll be sidelined for six-to-eight weeks," Bayern boss Hansi Flick said. "It hurts when a player of this quality is ruled out."
The injury is the latest setback in what's been a slow start to the campaign for Davies. The winger-turned-full-back has been benched for Hernandez following a stellar breakthrough season in which Davies played a vital role in Bayern's treble pursuit.
Hernandez, who moved to Bayern in 2019 from Atleti for a club-record €80-million fee, has started three of five matches in the league and the Supercup and DFL Supercup finals. Hernandez also started in Bayern's resounding midweek Champions League victory over Atletico Madrid.