The 32-year-old, who recently moved clear of Klaus Fischer to become the second-highest goalscorer in Bundesliga history, will consequently miss not only the pivotal Bundesliga title clash with RB Leipzig on Saturday, but also both legs of Bayern's Champions League quarter-final tie against Paris Saint-Germain.
Hansi Flick had nursed the Poland striker through a similar issue earlier in the campaign, notably resting him in two midweek Champions League group-stage matches, but the club confirmed that Lewandowski "has suffered sprained ligaments in his right knee" in a more damaging incident this time around.
Flick must now decide whether to trust Eric Choupo-Moting as a direct replacement in the central-striker role, or go with a less orthodox forward in the shape of Serge Gnabry or Thomas Muller, supported by both Kingsley Coman and Leroy Sane down the flanks.
Davies will miss two league matches after his straight red card in the 4-0 win against Stuttgart prior to the international break, while Boateng picked up his fifth booking of the season in that match.
Corentin Tolisso, Douglas Costa and Ron-Thorben Hoffmann remain on the treatment table for the foreseeable future, with youngster Tanguy Nianzou doubtful to feature against Leipzig, having only recently returned to training after a thigh injury.
Bayern Munich possible starting line-up: Neuer; Pavard, Sule, Alaba, Hernandez; Kimmich, Goretzka; Sane, Muller, Coman; Gnabry