Borussia Dortmund took full advantage as Bayern Munich and Schalke's respective challenges for the Bundesliga crown took huge dents after the title rivals suffered away defeats.
Kaiserslautern slipped to the bottom of the table, Hertha Berlin picked up an important win and Hamburg were hammered by Stuttgart.
Borussia Dortmund opened up a seven-point lead at the top of the Bundesliga with a 2-1 win over Mainz at the Westfalenstadion.
Jakub Blaszczykowski put the Westphalians ahead in the 26th minute and they missed numerous good chances to double their advantage before their former striker Mohamed Zidan levelled with 15 minutes remaining.
Shinji Kagawa scored the winner in the 77th minute as Dortmund took another step towards a successful defence of their Bundesliga title.
Bayer Leverkusen scored twice in the final 10 minutes to boost their own UEFA Champions League qualification prospects with a 2-0 home win over Bayern.
Stefan Kiessling broke the deadlock with 10 minutes to go before substitute Karim Bellarabi made the points safe in the final minute.
Schalke also slipped up on their travels after going down 2-1 at Freiburg, who moved off the foot of the table after just a fifth win of the season.
Sebastian Freis put Freiburg ahead after 18 minutes and Daniel Caligiuri's penalty on 66 minutes appeared to have the hosts cruising towards the points.
However, Teemu Pukki pulled a goal back for Schalke on 72 minutes before Lewis Holtby hit the post and then the visitors had Kyriakos Papadopoulos sent off.
Kaiserslautern are now propping up the rest of the division after being held to a 0-0 draw at home by Wolfsburg.
Nikita Rukavytsya's 62nd minute goal boosted Hertha's survival hopes following a 1-0 home success over Werder Bremen.
Jan-Ingwer Callsen-Bracker converted a late penalty as struggling Augsburg snatched a 2-2 draw away to Hannover.
The visitors had taken a 12th minute lead through Axel Bellinghausen before Hannover levelled on 33 minutes through Karim Haggui.
Former Manchester United striker Mame Biram Diouf gave Hannover the lead on 69 minutes before Callsen-Bracker kept his nerve from the spot a minute from time.
Zdravko Kuzmanovic scored a penalty in each half as Stuttgart enjoyed a convincing 4-0 win away at Hamburg.
January signing Vedad Ibisevic opened the scoring midway through the first half before Kuzmanovic netted from the spot on 31 minutes.
Kuzmanovic was on target from 12 yards again two minutes after half-time and Martin Harnik scored a late fourth after Hamburg's Jose Paulo Guerrero had earlier been sent off.