Bayern Munich midfielder Joshua Kimmich said his side need to question their mentality after they slumped to a shock 4-2 defeat at Bundesliga minnows Bochum ahead of Wednesday's Champions League clash with Red Bull Salzburg.
Bayern conceded four goals in the first half for the first time in a Bundesliga match since 1975 as promoted side Bochum rampaged to a stunning win, leaving the perennial champions stunned.
"This was our worst performance of the season. We need to ask ourselves whether this is the mentality which Bayern Munich embodies," a dejected Kimmich told Sky.
"Luckily it's happened in a Bundesliga match this time, but we have a Champions League game on Wednesday," he added.
Bayern had not lost to Bochum since 2004 ahead of this game, and beat them 7-0 when the two teams last met in September.
When Robert Lewandowski bundled in the opener for Bayern on nine minutes, it seemed like it would be a normal afternoon for the perennial champions.
But Bochum equalised quickly through Christopher Antwi-Adjei, before taking control in a frenzied 10 minutes before the break.
Juergen Locadia gave the hosts the lead from the penalty spot after a Dayot Upamecano handball, and an unsettled Bayern wilted under pressure.
Cristian Gamboa smashed the ball into the top corner from the edge of the area two minutes later, before Holtmann curled in another brilliant long-range effort on the stroke of half-time.
Lewandowski pulled a goal back in the second half, but it was too little for Bayern to avoid a fourth league defeat of the season.
After a week in which German football was discussing the idea of a new play-off format to combat Bayern's relentless dominance, recently promoted Bochum delivered a brutal reminder that the champions are not unbeatable.
Yet Bayern remain nine points clear at the top of the table overnight, ahead of Borussia Dortmund's trip to Union Berlin on Sunday.
Fuerth grab rare win
Elsewhere, struggling giants Wolfsburg and Borussia Moenchengladbach both pulled away from the relegation zone with timely wins.
Wolfsburg beat former coach Oliver Glasner with a 2-0 win at Eintracht Frankfurt, a Max Kruse penalty and a late goal from Dodi Lukebakio handing them a second successive win.
Manu Kone and Jonas Hofmann gave Gladbach a comfortable lead, before Iago pulled a goal back for fellow strugglers Augsburg.
Ramy Bensebaini restored the two-goal lead before Alfred Finnbogason snatched a late consolation goal.
Bottom club Greuther Fuerth gave themselves hope in the relegation fight with only their third win of the season against Hertha Berlin.
Branimir Hrgota opened the scoring after just 27 seconds and doubled the lead with a second-half penalty before Hertha's Linus Gechter scored his first Bundesliga goal late on.
Freiburg leapfrogged Union Berlin into sixth with a 1-1 draw at home to Mainz, substitute Nils Petersen cancelling out Alexander Hack's first-half opener.