Bayern Munich failed to take full advantage of Hamburg's defeat on Saturday, only drawing 2-2 with struggling Mainz.
Mainz took a shock 2-0 lead, Mohamed Zidan (9) and Manuel Friedrich (13) finding the back of the net before Bayern found their rhythm.
Roy Makaay pulled the Bundesliga leaders level before half time, firing home after 29 minutes before converting a penalty shortly after (37).
Surprisingly, Bayern failed to finish off their opponents in a dour second half, but they nonetheless extend their lead over nearest challengers Hamburg to five points with just three games of the season remaining.
The day's other game pitted third against fourth as Werder Bremen hosted Schalke at the Weserstadion, but neither were able to break the deadlock.
The 0-0 draw leaves Schalke six points behind Bremen, who will now be hoping to overhaul Hamburg and finish the season in second.