Dortmund increased their lead in the table to seven points with a 2-1 victory over Mainz. Earlier Leverkusen pulled off an unlikely 2-0 win over Bayern Munich, casting a major pall on the Bavarians' title hopes.
Despite a slight dip in form in the second half, Dortmund maintained their perfect record in 2012 with a close win over gutsy but overmatched Mainz.
Knowing they had a chance to pull away from Bayern, Jürgen Klopp's men piled on the pressure from the opening whistle and jumped in front in minute 26. Jakub Blasszczykowski latched on to a rebound and struck pay dirt.
To their credit, Mainz did not give up, while Dortmund seemed lulled into defending their advantage. And they were punished fifteen minutes from time, when former Dortmund striker and Klopp protege Mohamed Zidan beat keeper Roman Weidenfeller.
But just eighty seconds on, Shinji Kagawa lifted a low cross into the net to restore the hosts' lead. Robert Lewandowski should have hit the mark, too, slightly later, but uncharacteristically blew a sitter.
So the margin of victory was tighter than it should have been, but Dortmund won't care on a day where the other results went their way.
Bayern's bosses will be fuming after a match in which Munich began brightly, but failed to generate significant chances and deservedly lost in the end. Dortmund now have a chance to go seven points clear when they meet Mainz in Saturday's late match.
Franck Ribery started on the bench after picking up a slight thigh injury mid-week, but Bayern still owned the majority of possession in the first half. Mario Gomez had the best chance after he rounded Leverkusen keeper Bernd Leno, but his weak shot was blocked.
After the break Leverkusen coach Robin Dutt introduced a second striker, Eren Derdiyok, and that move paid off, with the hosts creating more shots on goal than Bayern, who seemed to tire. And with ten minutes to go Stefan Kiessling scored, after Bayern keeper Manuel Neuer failed to secure a cross.
Karim Bellarabi then caught the Bavarians out on the break just before time, as Leverkusen secured their first win in 15 attempts against German football's powerhouse.
And that was not the end of the upsets.
Points for Freiburg and Berlin
Schalke can now all but bury any residual hopes they had of challenging for the title, having fallen 2-1 in Freiburg.
Freiburg were the more committed side right from the off and were rewarded in minute 18 with a goal by Sebastian Freis. They doubled their advantage after the break after Daniel Caliguiri converted a penalty.
Substitute Teemu Pukki grabbed one back, but Schalke defender Kyriakos Papdopoulos was sent off, and Freiburg held on for a rare win. Schalke are now only four points clear of Leverkusen in the battle for the European spots.
Much further to the north, Hertha Berlin got their first points of 2012 and their first win under coaching legend Otto Rehhagel by beating Bremen 1-0.
Rehhagel's defensive mindset was on ample display as Hertha largely closed down Bremen's vaunted attack. Winger Nikita Rukavytsya's first-ever Bundesliga goal was all the hosts needed to seal three valuable points and move out of the relegation zone.
The win probably felt a bit strange for Rehhagel, as Bremen were the team with which he had his greatest Bundesliga coaching successes.
Horrible foul in Hamburg
Elsewhere in the league, Augsburg got off to a hot start against Hanover, generating four excellent scoring chances. But only Axel Bellinghausen converted, and Hanover equalized before the break, with Karim Haggui heading home a Christian Pander corner.
In the second half, Mame Diouf gave Hanover a brief lead, but just before the final whistle Jan-Ingwer Callsen-Bracker converted a penalty to ensure the visitors at least got something from the encounter. Still, the 2-2 draw means Augsburg drop back down to 16th in the table.
Stuttgart, by contrast, made the most of their early opportunities away in Hamburg. Vedad Ibisevic scored in minute 23 after a lovely solo move. And Zdravko Kuzmanovic converted a penalty eight minutes later.
The referee again pointed to the spot immediately after the restart, and Kuzmanovic found the mark for a second time to put the game beyond a weak Hamburg's reach. Slobodan Rajkiovic was at fault on both of the penalties.
Hamburg's Paolo Guerrero was then sent off for a nearly criminal challenge from behind on Stuttgart keeper Sven Ullreich. The striker faces a lengthy suspension, and a late goal by Martin Harnik completed the 4-0 humiliation.
Kaiserslautern went bottom of the table after slogging through a dull scoreless draw with Wolfsburg.
On Sunday, Mönchengladbach can move up to second place, ahead of Bayern, in their away match against struggling Nuremberg. And in the late match, Hoffenheim host Cologne.
Author: Jefferson Chase
Editor: Andrea Rönsberg