Werder Bremen midfielder Diego was red-carded as his second-placed side were beaten 1-0 by Eintracht Frankfurt on Saturday to give Bundesliga leaders Bayern the chance to open a six-point gap.
Brazilian Diego, one of the league's biggest drawcards, was shown a straight red card for a foul in the 40th minute and Greek striker Ioannis Amanatidis struck for the home side on 56 minutes to humble Bremen.
With Bayern in action against fourth-placed Hamburg at the Allianz Arena on Sunday, this would have been the last thing Bremen coach Thomas Schaaf wanted as Munich already had a three-point lead.
Two of the Bundesliga's struggling sides, VfB Stuttgart and Duisburg, both produced spirited performances to boost their flagging league positions and confidence.
Defending champions VfB Stuttgart picked up their second consecutive win at home to Karlsruhe to cancel out their two previous defeats as Germany's 2007 player of the year Mario Gomez curled in a fifth minute shot to get the ball rolling in the 3-1 victory.
Germany midfielder Roberto Hilbert then followed it up with right-footed shot in the 26th minute.
The visitors grabbed a consolation goal through Hungary midfielder Tamas Hajnal, before Brazilian striker Cacau sealed the win with a 89th minute strike to put his side eighth.
Duisburg lifted themselves off the bottom with a 2-0 win at Arminia Bielefeld after the heart-break of their 3-2 defeat at home to Stuttgart last week when the winning goal was conceded deep into injury time.
Duisburg's Silvio Schroeter put his side ahead in the eighth minute before Nigerian striker Manasseh Ishiaku hit a 48th minute goal.
After the heroics of their 1-0 Champions League win over FC Porto on Tuesday, Schalke were humbled 1-0 by Bayer Leverkusen by a spectacular long-range pin-point accurate shot by Germany defender Manuel Friedrich on 85 minutes.
The shot gave Schalke goalkeeper Manuel Neuer no chance as it flew into the top of the net and put Bayer third in the league.
In the day's other match VfL Wolfsburg were held to a 0-0 draw by Hertha Berlin.