Bayern Munich lost its third straight game - for the first time in more than 10 years - 3-1 at Hannover in the Bundesliga to put coach Louis van Gaal's future in doubt on Saturday.
"We're now in a situation which is very worrying for Bayern Munich. We have to sleep on it and see how we proceed."
Mohammed Abdellaoue and Konstantin Rausch gave Hannover a 2-0 lead before Arjen Robben pulled one back in the 55th minute.
Sergio Pinto restored Hannover's two-goal advantage when goalkeeper Thomas Kraft was unable to hold on to his powerful long-range effort.
Bayern defender Breno was sent off in the 73rd.
"The players are very disappointed, the club is disappointed, the coach is disappointed. Everyone is disappointed because we expected something else," Van Gaal said.
"I've always received the backing of my club and they decide whether to continue giving this backing or not - not me."
With nine games left to play, Hannover has five more points than fourth-place Bayern.
Bayer Leverkusen, in second, enjoyed a comfortable 3-0 home win over Wolfsburg in Saturday's late game, when Michael Ballack was left out of the squad by coach Jupp Heynckes.
Sidney Sam's wonderful through ball allowed Lars Bender to claim his first Leverkusen goal in the 21st, and Renato Augusto and Stefan Kiessling completed the scoring in the first half.
Augusto should have scored his second in the 58th when he shot straight at Diego Benaglio, and the goalkeeper denied Sam following a Leverkusen counterattack in the 67th.
Wolfsburg, the 2009 champion, remains one point above the relegation zone.
Earlier, Stuttgart won two games in a row for the first time this season, moving provisionally out of the relegation zone on goal difference after a 1-0 home win over 10-man Schalke.
Benedikt Hoewedes was sent off in the 14th, when referee Felix Brych ruled he stopped Tamas Hajnal's shot with his arm despite lying on the pitch. The unlucky defender received a straight red card and Zdravko Kuzmanovic dispatched the resulting penalty.
Raul Gonzalez almost equalized before the interval, narrowly missing with a header from Jefferson Farfan's cross.
Stuttgart's appeals for a second goal - when goalkeeper Manuel Neuer let Christian Gentner's shot slip through his hands before recovering to catch the ball on the line - were turned down in the 70th.
Christian Eigler scored four as Nuremberg beat visiting St. Pauli 5-0.
The hosts raced into a three-goal lead in the first 20 minutes, with Eigler scoring twice after Philipp Wollscheid's third-minute opener.
He completed his hat trick in the 86th, and added another goal a minute later to complete a miserable afternoon for Holger Stanislawski's side.
Filip Daems scored a penalty and Igor de Camargo sealed a 2-0 win for bottom side Borussia Moenchengladbach at home to Hoffenheim.
Eintracht Frankfurt, yet to score in 2011, and winless Kaiserslautern each maintained their unenviable records in a 0-0 draw.
"Exceptional. We were brave today," Hannover coach Mirko Slomka said. "We're fighting for our position in the table, we're fighting hard."
Hannover made it 15 wins this season with victory over Bayern, which started hesitantly.
A lost ball in midfield paved the way for the opener in the 16th. Hannover countered quickly with Rausch whipping the ball in for Abdellaoue to prod it past Kraft from eight meters (yards).
Abdellaoue put in another dangerous cross moments later, but none of his teammates were there to take advantage.
Bayern looked out of sorts in the face of the home side's pressing game. Emanuel Pogatetz had another chance from a corner in the 30th, when he placed his header straight at Kraft.
Rausch doubled Hannover's lead in the 51st, when he blasted an angled shot past the goalkeeper from 14 meters.
Thomas Mueller had a penalty appeal waved away moments later, after a challenge from Hannover's American defender, Steven Cherundolo, and Abdellaoue went close again at the other end.
A rare header from Robben pulled Bayern back into the game in the 55th after being left unmarked at the far post to nod in Franck Ribery's cross from close range.
However, Kraft was unable to stop Pinto's effort creeping over the line in the 62nd, before Robben hit the side-netting and was denied by Ron-Robert Zieler.
Breno was sent off when his reaction to a challenge from Lars Stindl earned him a direct red from referee Jochen Drees.
"We played a very good game in Milan 10 days ago," Van Gaal said. "Within ten days we have given away so much. That increases the pressure from outside, and the players feel that too."
