German champions Bayern Munich were stunned by a 96th-minute winner from third division Saarbrucken in the German Cup.
Marcel Gaus scored late into stoppage time to earn a famous victory.
Muller had put Bayern ahead but Patrick Sontheimer equalised before Gaus' memorable winner.
It is the third time in four years in which Bayern - who have won the Bundesliga title in each of the last 11 seasons - have exited the German Cup in the second round, the stage at which top division sides enter the competition.
Bayern, who travel to Bundesliga rivals Borussia Dortmund on Saturday, also lost central defender Matthijs de Ligt to a serious-looking knee injury early in the match, leaving the side with only one fit centre-back.
Muller looked to have Bayern on track for a routine victory when he opened the scoring on 16 minutes, before De Ligt's injury forced midfielder Joshua Kimmich into defence and appeared to unsettle Bayern.
Saarbrucken grew in confidence and equalised in first-half stoppage time, Sontheimer tapping in a pass from Lukas Boeder after Bayern midfielder Frans Kratzig was forced into a mistake.
Instead, the England captain was warming up as extra-time approached when 34-year-old left back Gaus produced a moment that will go down in German football history.