Vincent Kompany had one eye on Tuesday's Champions League til against title rivals Bayer Leverkusen, making 10 changes for the visit of relegation-battling Bochum.
That decision looked sensible enough after 28 minutes, as Raphael Gueirrero scored twice either side of a Serge Gnabry miss from the penalty spot. The Portuguese rifled home a loose ball in the opposition box to open the scoring on 14 minutes, before doubling the lead in the 28th with a headed finish. Gnabry, covering for usual penalty taker Harry Kane, struck the woodwork from 12 yards out.
Bochum forced their way back into the game within three minutes. Jakov Medic marked his first Bundesliga with a thunderous effort. The momentum was firmly with the visitors as Joao Palhinha was dismissed for a studs up challenge minutes before the break.
Ibrahima Sissoko nodded the game level in the 51st minute and the visitors completed their stunning comeback 20 minutes later when Matus Bero slid a cool finish past the debuting Jonas Urbig in the Bayern goal. Kompany called on the cavalry, sending superstars like Kane and Jamal Musiala into the fray. Even with their best attackers on the field, the Bavarian giants couldn't break Die Unabsteigbaren's rearguard action.