Werder Bremen moved above Mainz in the Bundesliga table with a 2-1 win in an entertaining game at the Weser Stadion.
Aaron Hunt scored both goals for Thomas Schaaf's men, the second coming late in the game to render Adam Szalai's earlier equaliser worthless for Thomas Tuchel's side.
Bremen have now picked up seven points in their last three games while Mainz lost for the first time since September 25.
Bremen are more used to challenging for a place in Europe than Mainz, but the two sides came into the game with roles somewhat reversed.
A win for Mainz would have taken them ahead of defending champions Dortmund, with defeat leaving Bremen just three points above the relegation zone.
However, with the Bundesliga still so tightly packed behind the top three, the opposite result would have seen the sides swap places in the table, and that is precisely what happened.
Szalai, who scored a hat-trick last weekend, set up Nicolai Muller for the first chance in the eighth minute and he beat Sebastian Mielitz with a lob which just went wide of the goal.
A more familiar reality was established in the 10th minute when Hunt put Bremen ahead, shooting high into the top right-hand corner of the goal after Nils Petersen squared the ball to him level with the penalty spot.
Mainz had another gilt-edged chance in the 12th minute when Muller this time hit the target, but Mielitz made an excellent save.
Eljero Elia hit the post as the chances came thick and fast at both ends of the field, with the 39,114 fans at the Weser Stadion getting their money's worth within the first quarter of an hour.
Andreas Ivanschitz's header was turned wide by a busy Mielitz, who was helpless as Szalai brought Mainz level in the 64th minute, looping a header past the Bremen goalkeeper from Radoslav Zabavnik's cross.
Both sides scented a winner, but Bremen got it through Hunt's direct free-kick in the 85th minute.
Christian Wetklo should probably have made a better attempt at keeping the ball out as Hunt curled his shot over the wall and in for three points.