Bayern Munich lost for the third time in a week as Raul Bobadilla's strike clinched a 1-0 victory which boosts Augsburg's hopes of qualifying for the Europa League.
Despite having the second leg of their tie with Barcelona to prepare for, Pep Guardiola selected the majority of his key players on what proved to be another disappointing day for the Bundesliga champions.
Augsburg were handed a huge boost in just the 13th minute when Pepe Reina, who was making a rare start in goal for Bayern, charged off his line to bring down Bobadilla inside the box, and the Spaniard could have no arguments with the red card which followed.
Manuel Neuer was forced off the bench to face the penalty, but the World Cup winner was not needed to make a save as Paul Verhaegh wasted a great chance by striking the post.
Despite the disappointment from the spot, Augsburg continued to ask questions of the champions as the lively Bobadilla fired just over from a promising position.
However, Bayern improved as the first half progressed and, after Mario Gotze had threatened on two occasions, they came agonisingly close to the opener before the break when Robert Lewandowski's effort clipped the crossbar.
The Polish striker threatened again after the break as he shrugged off a couple of challenges before unleashing a shot which was pushed to safety by Marwin Hitz.
Augsburg's goalkeeper was forced into action again a few moments later as Mitchell Weiser, a constant threat out wide, struck a powerful effort which forced Hitz into a crucial stop.
Despite looking comfortable for much of the second half, the 10 men were behind when Pierre Hojbjerg sprinted clear before crossing to Bobadilla, whose clever back-heel was enough to beat Neuer.
Clever play from Sascha Molders could have provided a second late on, but Augsburg managed to hold on for all three points.
Callum Mulvihill
