Werder Bremen pulled off a shock 5-2 win at Bayern Munich on Saturday, humiliating the champions in front of their own fans and giving Juergen Klinsmann his first taste of defeat as a Bundesliga coach.
Markus Rosenberg struck twice to lead the rout as Werder took a 5-0 lead before Tim Borowski pulled two back for the embarrassed Bavarians.
"It was a black day," Klinsmann told reporters after Bayern's first defeat of the season denied them top spot. "We really took one on the nose."
Instead Schalke 04 moved into first place with 11 points from five matches after a 1-0 win at home to Eintracht Frankfurt, courtesy of an own goal from Patrick Ochs.
Hamburg SV, in second place on 10 points, will recapture top spot if they win at Wolfsburg on Sunday.
Bayer Leverkusen are third on nine points following their 4-0 win at home to Hanover 96 on Friday, while Werder are fourth and Bayern fifth on eight points apiece.
Werder, runners-up to Bayern last season, came into the game chastened by their failure to find the net in a goalless draw with Anorthosis Famagusta in the Champions League on Tuesday.
They had no such problems against Bayern, as they punished mistakes from the defence and hapless keeper Michael Rensing.
After a few near misses they took the lead after half an hour when Mesut Ozil rolled a pass through the Bayern centre-backs for Rosenberg to collect and slip in his shot.
Naldo was left unmarked to tap in the second just before the break and Mesut blasted the third in under the bar nine minutes after the restart.
Bayern, who enjoyed a winning start to their Champions League campaign away to Steaua Bucharest, made certain of Werder's win when the defence left Claudio Pizarro free to score against his old club, before Rensing's missed punch presented Rosenberg with his second.
"Bremen were better, fresher and more aggressive than us," said Klinsmann, who is in his first season in charge. "We just have to try and learn from this."