Hamburger SV grabbed the provisional lead in the German Bundesliga when it ended Bayern Munich's 11-game, four-month unbeaten run 1-0 in the first match after the six-week winter break on Friday.
Mladen Petric earned the only goal a minute before halftime in Hamburg.
Hamburg's third straight victory and fifth game without a loss gave the northern club 36 points through 18 matches.
Bayern, which last lost on September 27, remained on 35 points in third place.
Hoffenheim was second with 35, and can regain the lead with victory at home against Energie Cottbus later yesterday.
"We are all overjoyed," Petric said.
"This was a great team performance. We dominated the first half, and Bayern pressured us in the second half. But we stuck together. This victory does us a lot of good. But we know from experience that the next game will be tough (against Karlsruhe)."
Bayern coach Juergen Klinsmann didn't mask his disappointment.
"We wanted so much more from this game," he said. "And we had so many chances but the ball just didn't want to go in.
"We just have to get our points in other games now."
Hamburg coach Martin Jol used speedy midfielder Jonathan Pitroipa and a well-organized defence to stifle playmaker Franck Ribery's creativity in the first half.
Piotr Trochowski gave Bayern the first scare, as his long shot in the sixth minute was barely deflected off the left post by goalkeeper Michael Rensing.
The defending champion appeared to grab the lead in the 28th through Luca Toni, but he was ruled to have fouled Hamburg defender Bastian Reinhardt before his shot.
Most of the rest of the first half was spent in the midfield until Hamburg midfielder David Jarolim shot from about 21 meters. Rensing was able to fist away the low shot but the ball went only to Petric, who headed it back over the Bayern 'keeper for the goal.
Hamburg nearly doubled the lead just 34 seconds into the second half as Jose Paolo Guerrero sent a throughball to Petric, who poked a ball past a charging Rensing but only against the right post.
In Bayern's push for the equalizer. Hamburg goalie Frank Rost batted away a Miroslav Klose header in the 48th.
Klose and Toni missed further opportunities to equalize before Klinsmann threw on a third striker, Landon Donovan, on loan from the Los Angeles Galaxy, to pile on the pressure.
Despite several more chances they failed to get the equalizer.
"It was a tough match," Jol said. "We had a bit of luck in the second half but overall, 1-0, I think is in order."
"We have plenty to blame ourselves," Bayern defender Philipp Lahm said. "It's very disappointing that we created so many chances but could not convert any of them and bring home at least one point."
(Agencies via Shanghai Daily Feburary 1, 2009)
