Second-placed Borussia Dortmund fell into the trap of a 3-2 defeat at Hertha Berlin on Saturday, leaving it nine points behind Bundesliga leaders Bayern before the start of the winter break.
Marco Richter scored two goals in the second half to turn Hertha from behind with a goal and advance 3-1.
Dortmund, who were seeking to close the gap with Bayern after the defending champions’ 4-0 victory over Wolfsburg on Friday, were the better side at the start, despite the absence of in-form Judd Blingham, defender Mats Hummels and goalkeeper Gregor Kopel ill.
Dortmund had several chances before Julian Brandt opened the scoring with a shot over goalkeeper Alexander Shuvolov in the 31st minute.
Herta bounced back and equalized through Isaac Beloufdel with a shot from the bottom of goalkeeper Marvin Hitz, six minutes after the break.
Richter gave the hosts a 2-1 lead in the 57th minute with a superb shot in the top corner.
The 24-year-old striker completed the hat-trick in the 69th minute after a mistake by Brandt at the edge of the penalty area.
Substitute Stephen Teigen cut the difference for Dortmund with a header seven minutes from the end.
Dortmund remained in second place with 34 points, nine points behind Bayern.