Interim Bayern coach Hansi Flick suffered his first defeat in five games with a shock 2-1 loss at home to Bayer Leverkusen.
Berlin: Manuel Neuer says a second consecutive defeat is unthinkable for Bayern Munich on Saturday at Bundesliga leaders Borussia Moenchengladbach, who quietly harbour aspirations of a first German title since 1977.
Bayern have lifted the trophy each of the past seven seasons but their Bundesliga reign is under threat as they sit fourth -- four points behind Gladbach with a third of the season played.
Interim Bayern coach Hansi Flick, who replaced the sacked Niko Kovac last month, suffered his first defeat in five games a week ago with a shock 2-1 loss at home to Bayer Leverkusen.
Neuer has called for a response by Bayern at Borussia Park.
"We simply must not lose, that's out of the question - we're going there to win," the Germany goalkeeper told Kicker magazine.
Under new head coach Marco Rose, Gladbach are this season's surprise package and have spent the last two months in first place.
Swiss striker Breel Embolo scored twice in Sunday's 4-2 home win against Freiburg to keep Gladbach top, bouncing back from a surprise 2-0 away defeat at Union Berlin.
A win over Bayern would go some way to firming up Gladbach's status as genuine title contenders, especially with second-placed RB Leipzig, who host mid-table Hoffenheim on Saturday, just a point behind.
"We always want to compete with the best - and Bayern are the best," said Embolo.
"But it's not just us who want to stand up to them. Leipzig, Schalke and Leverkusen want that too.
"It's going to be a top game. Bayern are a world-class team and we need to hope for a good day."
Another defeat would pile the pressure on Bayern and Flick. Ex-Germany coach and Gladbach legend Berti Vogts said his former side "will be hard to knock off top spot" if they beat the Bavarians this weekend.
Gladbach fans can already be heard at matches singing about becoming German champions as they enjoy their best start to a season since 1977 -- the last time they won the Bundesliga.
"We feel good at the moment and spirits are high, we are going into the duel with respect, but know we have a chance to win," said Rose.
Germany defender Matthias Ginter is expected to be fit again after injury to face Bayern, who are near full strength.
One to watch: Christopher Nkunku
The France Under-21 midfielder grew frustrated at a lack of opportunities at Paris Saint-Germain, the club he joined aged 13, but a summer switch to RB Leipzig has enabled him to unlock some of his potential this season.
Nkunku has scored once and laid on five assists in a dazzling run of form over his past four league games.
"I wouldn't say it was easy for me to leave PSG, but it's good for my development," he told Kicker ahead of the visit of Hoffenheim.
Nkunku has found his feet in Germany, admitting it was tough at PSG where he was in the shadows behind the likes of Kylian Mbappe and Neymar.
"I did play, but only when one of the stars was injured, suspended or rested. That wasn't enough for me."
11 - Bayern Munich have hit the woodwork 11 times so far this season -- most in the league -- and nearly double that of nearest rivals Schalke and Moenchengladbach (six).
24 - Gladbach's wins in 102 league games against Bayern. They have lost 49 of those meetings with 29 draws.
62 - Robert Lewandowski's shots so far this season, resulting in 16 league goals for Bayern.
Fixtures (all times 1430 GMT unless stated)
Friday: Eintracht Frankfurt v Hertha Berlin (1930)
Saturday: Borussia Dortmund v Fortuna Duesseldorf, RB Leipzig v Hoffenheim, Borussia Moenchengladbach v Bayern Munich, Freiburg v Wolfsburg, Augsburg v Mainz, Bayer Leverkusen v Schalke 04 (1730)
Sunday: Union Berlin v Cologne, Werder Bremen v Paderborn (1700)