Bayern will be confirmed champions with a win on Saturday if second-placed Borussia Dortmund lose at relegation-threatened Fortuna Duesseldorf earlier in the day.
That scenario would give Hansi Flick’s side an unassailable 10-point lead with three games remaining. But Bayern are without Lewandowski, the league’s top scorer this season with 30 goals, and Muller, who is one short of the Bundesliga record of 21 assists in a single campaign.
“It’s annoying, but we can’t do anything about it,” said Bayern coach Flick.
Thiago Alcantara is likely to replace Muller, while winger Serge Gnabry could take Lewandowski’s place up front if he is fit after a back injury.
Bayern proved they can score goals without Lewandowski by thumping Hoffenheim 6-0 in late February when the Polish striker was injured.
They had a scare in Wednesday’s German Cup semi-final win over Eintracht Frankfurt, when Danny da Costa equalised for the visitors before Lewandowski sealed a 2-1 win with his 45th goal this season.
Muller admitted Bayern were “tired”, “worn out” and scrapped their way to victory in the first of three games in six days.
But they are still in the running to repeat their 2013 treble having beaten Chelsea 3-0 away in their Champions League last-16 first leg before the competition was suspended in mid-March due to the coronavirus pandemic.
Fourth-placed Gladbach pulled off a shock 2-1 victory at Borussia Park when the sides met last December.
But Marco Rose’s side have been erratic of late, crushing Union Berlin 4-1 at home at the end of May before stumbling to defeat at Freiburg last weekend. Rose hopes to include Swiss forward Breel Embolo, with the 23-year-old fit after an ankle knock.
Bremen’s basement battle
At the foot of the table, fallen giants Werder Bremen face a crucial game at Paderborn in a battle of the bottom two.
Florian Kohfeldt’s Bremen are six points from safety in 17th and three off the relegation play-off place following back-to-back home defeats.
Bremen, who were in the Champions League a decade ago, have spent more seasons in the top flight than any other club, but are running out of time.
“We know how much is riding on this game,” said American forward Josh Sargent. “This club has such a long history, and no one wants to let the team or the city down.”
One to watch: Emre Can
The Germany international scored the winner in last weekend’s tense 1-0 win over Hertha Berlin despite playing as part of a back three.
The 26-year-old, who usually plays in midfield, has been a reliable figure for Dortmund since joining from Juventus in January.
He has shown his versatility by adding steel to a sometimes vulnerable side while still providing an attacking threat, having also marked his debut in February with a stunning long-range strike against Bayer Leverkusen.