Bayern Munich suffered a surprise defeat by Mainz as Borussia Dortmund boosted their Bundesliga title hopes going into Saturday’s Der Klassiker.
Dortmund, who beat Darmstadt 2-0, are now five points off Bayern and host the champions this weekend.
Bayern, who had won 17 consecutive home games in all competitions, trailed when Mainz’s Jairo swept home a cross.
Arjen Robben levelled from 25 yards but substitute Jhon Cordoba scored a late winner from outside the box.
Dortmund, who have now won six of their last seven Bundesliga matches, beat Darmstadt thanks to goals from Adrian Ramos and Erik Durm.