Bayern Munich suffered their first home defeat since April as Borussia Dortmund closed the gap at the top of the Bundesliga to five points.
Bayern fell to only their second defeat of the season as fifth-placed Mainz blew the title race wide open with a 2-1 win in Bavaria.
Mainz who drew first blood with Jairo Samperio meeting Giulio Donati's cross and beating Manuel Neuer from 10 yards.
The equalising goal came in the second half with Arturo Vidal squaring for Arjen Robben, whose 20-yard effort beat Loris Karius low into the bottom corner.
The winner came in the 86th minute as Julian Baumgartlinger played the ball square to Jhon Cordoba who, with only Mainz's second shot of the second half, beat Neuer from 15 yards and sent the Allianz Arena into an eerie state of silence.
On Saturday, Dortmund host Bayern and could move within two points and create an unexpected Bundesliga title race in Pep Guardiola's final season at the helm.
Borussia Dortmund warmed up for the Klassiker with a 2-0 win at Darmstadt.
Adrian Ramos and Erik Durm scored for the Westphalians, who were playing their fifth game in 14 days but showed little sign of the strain as they dominated from start to finish.
Dortmund coach Thomas Tuchel made no fewer than eight changes to his side with Roman Weidenfeller starting in goal and 17-year-old Felix Passlack handed his debut.
Dortmund took the lead with Pierre-Emerick Aubameyang's header bringing a save out of Christian Mathenia, but he could only parry the ball out for Ramos to convert from close range.
Durm got on the scoresheet from Gonzalo Castro's pass to double Dortmund's lead in the 53rd minute.
Borussia Monchengladbach kept up their push for a place in the Champions League next season with a 4-0 win over Stuttgart which effectively ends their opponents' slim hopes of qualifying for Europe next season.
Thorgan Hazard gave Gladbach the lead in the 16th minute when he turned in Fabian Johnson's low cross from the right.
Lars Stindl should have added a second 20 minutes later, but he missed an open goal after Raffael had rounded Stuttgart goalkeeper Przemyslaw Tyton, while the woodwork prevented Hazard from adding a second just before the interval with Tyton turning his shot onto the underside of the crossbar.
Raffael added a second on the hour mark as Gladbach's dominance was finally reflected in the scoreline, before Patrick Herrmann, back on the field for only the second time after a long injury absence, made it three only seconds after coming on.
An own-goal from Kevin Grosskreutz compounded Stuttgart's woes as they were beaten for the second game in a row, all but ending any slim hopes they had of getting into the race for a place in Europe next season.
Claudio Pizarro rolled back the years to hit a hat trick for Werder Bremen as they relieved themselves of some relegation worries with a 4-1 win at an out-of-sorts Bayer Leverkusen.
Fin Bartels was also on target for the northern Germany side, who provided Leverkusen's consolation themselves through a Papy Djilobodji own goal.
The result lifts Viktor Skripnik's men out of the bottom three and dents Leverkusen's hopes of qualifying for the Champions League next season.
Hertha Berlin held onto third place and strengthened their hopes of playing in the Champions League with a 2-0 win over Eintracht Frankfurt.
After Frankfurt had thwarted their attacks in the first half, Hertha took the lead after just over an hour with Mitchell Weiser powering in Salomon Kalou's pass.
Kalou added the second himself in the 78th minute, racing away from Carlos Zambrano before slotting the ball in past Lukas Hradecky to keep the Old Lady three points ahead of Borussia Monchengladbach and Mainz.
Schalke bounced back from some recent poor results with a dominant performance and 3-2 win over 10-man Hamburg which keeps their hopes alive of qualifying for the Champions League next season.
Hamburg could hardly have imagined making a better start to the game with Roman Neustadter gifting them the lead in the fourth minute, as he misjudged a long ball forward and allowed Nicolai Muller to get in behind him and divert the ball past Ralf Fahrmann.
Schalke hit back and had it not been for some heroics from Hamburg goalkeeper Rene Adler, the hosts would have levelled sooner than they actually did.
Max Meyer finally brought the Royal Blues back on terms in the 38th minute with a shot from almost 25 yards out before Hamburg were reduced to 10 men with Johan Djourou picking up a second yellow card on the stroke of half-time.
Klaas-Jan Huntelaar put Schalke in front midway through the second half when he headed in a cross from Alessandro Schopf, who added the third with a deflected shot in the 77th minute.
Gojko Kacar pulled one back for Hamburg in stoppage time but it was too little, too late for the northern Germany side.
Hoffenheim boosted their survival hopes with a 2-1 win over Augsburg which drags the Bavarians into danger at the bottom of the table.
Kevin Volland put Hoffenheim in front midway through the first half when Marwin Hitz was unable to hold onto an Eduardo Vargas shot which came back at him off the post and Patrick Ochs picked up the loose ball to set up the striker.
Augsburg levelled before half-time with their captain Paul Verhaegh converting a penalty after Niklas Sule handled the ball inside the area.
Mark Uth put Hoffenheim back in front with less than 10 minutes still to be played, turning in Andrej Kramaric's cross having earlier hit the post, and it was enough to earn Julian Nagelsmann's men all three points and take them just two away from the relegation playoff berth and four behind their guests.