(CNN) -- Champions League high-flyers Schalke have been dumped out of the German Cup after a home defeat to lowly Mainz.
Schalke, who reached the last 16 of Europe's elite club competition by topping their group, sacked coach Huub Stevens on Sunday.
And in his first game in charge as caretaker coach Jens Keller saw his side go down 2-1 in the German Cup -- a competition they won in 2011 -- as an 83rd minute winner from Nicolai Muller settled the tie.
Marco Caligiuri opened the scoring for Mainz in the first half but Dutch international Klaas-Jan Huntelaar equalized for Schalke with 15 minutes to go before Muller struck.
It continues a miserable run of form that has seen Schalke take just two points from a possible 18 in the Bundesliga. They currently trail league leaders Bayern by 17 points.
Bayern had no such trouble as they beat Augsburg 2-0, though they did play for the majority of the second half with ten men after France international Franck Ribery was sent off.
Mario Gomez registered his fourth goal in six games upon returning from an ankle injury and Switzerland's Xherdan Shaqiri made sure of the win.
There was another shock as Third Division side Offenbach knocked out Bundesliga opposition in the form of Fortuna Dusseldorf. Freiburg beat Karlsruhe 1-0.