Borussia Dortmund missed the opportunity to climb to third in the Bundesliga as Mainz struck late to earn a 1-1 draw on Sunday.
With Hoffenheim beaten at second-placed RB Leipzig earlier in the weekend, Dortmund could not capitalise fully despite leading for 80 minutes and sit fourth, a point behind Eintracht Frankfurt.
Marco Reus' 11th league strike against Mainz - more than against any other club - put Dortmund ahead after three minutes, but coach Thomas Tuchel was denied victory against his former club when Danny Latza equalised with seven minutes remaining.
It was a heady blow for Dortmund, who had seemed set for back-to-back wins after ending 2016 with four consecutive draws in all competitions.
Instead, this was to be another stalemate and any lingering hopes of a title challenge are surely over now, with the gap to leaders Bayern Munich at 14 points.
Tuchel welcomed Pierre-Emerick Aubameyang back into his side, following Gabon's early exit from the Africa Cup of Nations, and the Dortmund front-line soon combined to devastating effect.
After three minutes, Aubameyang's movement dragged defenders away for Andre Schurrle to play in Reus and the Germany international coolly finished beyond Jonas Lossl.
Further first-half attacks lacked the same cutting edge, but Lossl saved comfortably from Raphael Guerreiro and was on hand to sweep up a number of dangerous forward passes.
The Mainz goalkeeper was fortunate not to concede again, though, before the break, this time misreading Reus' teasing ball to Aubameyang and escaping as the division's top scorer failed to work an angle to shoot into the empty goal.
A corner was Lossl's only punishment and Sokratis Papastathopoulos' first-time blast was deflected away before the unmarked Lukasz Piszczek nodded over.
But Dortmund seldom looked like paying for this profligacy in the early part of the second half as Mainz created little and Niko Bungert directed a rare header wide.
Schurrle volleyed narrowly past the post at the other end and later shot straight at Lossl, but, in a game starved of quality, the key clashes were becoming increasingly physical.
Jairo Samperio and Schurrle both went into the book for an off-the-ball confrontation that saw them touch heads, while Mainz threw on the giant figure of Aaron Seydel to offer an aerial threat.
However, rather than the big forward, it was Latza who came storming onto Levin Oztunali's swirling cross and rattled in an equaliser seven minutes from time.
And Mainz almost stole all three points as Seydel held the ball up for Pablo De Blasis to drag just wide with the very last kick.
Key Opta stats:
- Reus scored the earliest goal in all competitions for Dortmund this season (3rd minute).
- Since coming back from injury, Reus had a hand in 9 goals (5 goals, 4 assists) in only 520 minutes of action - a ratio of once every 58 minutes.
- Marcel Schmelzer made his 300th appearance in all competitions for Dortmund, a milestone only 12 other players reached before.
- For the first time ever, star players Pierre-Emerick Aubameyang, Marco Reus and Andre Schurrle were on the field together for Dortmund in a league game.