The result in Werder Bremen is good news for defending champions Bayern Munich, the only team in the league's top six to win this weekend
Werder Bremen's Bundesliga title aspirations suffered a huge reality check on Sunday as they were smashed 6-2 at home by Bayer Leverkusen with Germany winger Karim Bellarabi in outstanding form.
The result in Bremen is good news for defending German champions Bayern Munich, the only team in the league's top six to win this weekend.
Bayern ground out a 2-1 win at Mainz on Saturday as their main rivals failed to pick up three points.
Leaders Borussia Dortmund drew 2-2 at home to Hertha Berlin on Saturday after Borussia Moenchengladbach, who are third, lost 3-1 at Freiburg on Friday.
Fourth-placed Bremen could have leap-frogged Bayern into second with a victory against Leverkusen, but instead suffered a nightmare first half and were 3-0 down at the break.
"We have forgotten one aspect of football -- to cover and prevent counter-attacks," admitted Bremen coach Florian Kohfeldt.
"This is a bitter defeeat and hurts, but we won't let it upset us."
Striker Kevin Volland scored Leverkusen's first goal after just eight minutes when he turned Bellarabi's cross into the net.
Bellarabi played a key part in the second when his low cross fell to Julian Brandt, who slammed his shot into the net seven minutes from the break.
Leverkusen's third came just before the half-time whistle when Volland spotted Bellarabi unmarked on the right and he chipped Bremen's onrushing goalkeeper Jiri Pavlenka.
After the break, Bremen coach Florian Kohfeldt hauled off left-back Marco Friedl, guilty of too many wayward passes, and brought on 40-year-old striker Claudio Pizarro, who briefly inspired a fightback.
Bellarabi nearly made it 4-0 by hitting the post early in the second half before going off and Pizarro pulled a goal back by tucking Davy Klaassen's well-timed pass into the net with an hour gone.
Japan striker Yuya Osako added a second two minutes later when he tapped home a corner.
However, Leverkusen took the wind out of Bremen's sails with three more goals.
Kai Havertz added their fourth when Pizarro lost possession and the 19-year-old sprinted away, dinking his shot over Pavlenka on 67 minutes.
The Bremen goalkeeper was responsible for Leverkusen's fifth goal when he failed to punch clear a corner and Aleksandar Dragovic tapped home before Havertz flicked in his sixth goal of the season.
Pavlenka prevented the scoreline becoming any more inflated with two late saves.
This was Leverkusen's first league win since September which pulled them up to 12th.
"I hope the team can take some momentum from this win," said Leverkusen's relieved coach Heiko Herrlich, who had been under pressure.
Earlier on Sunday, fifth-placed RB Leipzig were held to a goalless draw at home to strugglers Schalke, who stayed out of the bottom three.
Leipzig had the ball in the Schalke net early in the second half, but Yussuf Poulsen was flagged for offside.
Elsewhere, Germany goalkeeper Kevin Trapp was furious with his Eintracht Frankfurt side after only a 92nd-minute equaliser salvaged their recent unbeaten run in a 1-1 draw at Nuremberg.
Frankfurt are six games without defeat in all competitions after Sebastian Haller's late leveller, but Trapp was far from impressed.
"I don't know if we've won too much or if the mood (in the squad) was too good, but we can't go believing we'll just knock Nuremberg over like that," fumed Trapp on Eurosport.
"It was simply a bad performance from us."
Slovakia striker Adam Zrelak put Nuremberg ahead 12 minutes from time, moments after coming on to make his Bundesliga debut when he headed home at the far post.
However Frankfurt kept their composure and a last-gasp effort by Haller salvaged a point with his fifth goal this season.
Frankfurt are seventh in the league table while Nuremberg are down in 13th after victories against fellow strugglers Duesseldorf and Hanover 96.
Nuremberg 1 (Zrelak 78) Eintracht Frankfurt 1 (Haller 90+2)
RB Leipzig 0 Schalke 0
Werder Bremen 2 (Pizarro 60, Osako 62) Bayer Leverkusen 6 (Volland 8, Brandt 38, Bellarabi 45, Havertz 67, Dragovic 72, S. Langkamp 77-og)