Collective beats individuals: FSV Mainz 05 caused the first setback for Borussia Mönchengladbach under coach Daniel Farke with the 1-0 (0-0) away win.
A directly transformed free kick by Aarón (55th minute) ensured Mainz's fourth away win in a row against ten Borussia on Sunday.
Coach Bo Svensson's team thus equaled the club record that the Rheinhessen team had achieved under Thomas Tuchel in the 2010/2011 season.
With ten points now, FSV has moved past the undefeated Gladbachers in the Bundesliga table to fifth place.
With eight points remaining, Borussia fell back to ninth place after their first defeat under Farke.
Immediately before Mainz's winning goal, Gladbach's strong central defender Ko Itakura saw the red card for an emergency brake.
Bitter for the Gladbach team, where Farke had not included Julian Weigl and Nathan Ngoumou in the starting XI: Borussia should have been in the lead by then.
Top scorer Marcus Thuram became a tragic figure instead of a match winner.
The Frenchman missed seven of Gladbach's eight shots on goal in the first half and missed all of them.
Thuram, who was otherwise almost unstoppable at first, missed the biggest opportunity after a good half hour when he didn't use a bad air hole from Maxim Leitsch.
Running alone towards the strong Mainz keeper Robin Zentner, the attacker thought for too long and served weakly to Florian Neuhaus instead of shooting himself.
Dominik Kohr was able to clear one of the numerous slide tackles in Mainz that day.
The Rheinhessen played rustically and aggressively on the defensive and straightforward in attack from the start.
Borussia found it so difficult to raise their controlling ball possession game.
Despite the many good opportunities for Thuram, Gladbach coach Farke was extremely angry.
For the first time ever during his time as coach on the Lower Rhine, his team lost because the uncomfortable and strong-running Mainzers were better collectively and took the lead to the finish with a majority.
Again and again Farke scolded loudly on the sidelines, kicked medicine kits or hammered on the roof of the players' bench.
But he only set personal accents out of necessity.
Marvin Friedrich replaced the ailing Nico Elvedi in central defense and a little later Captain Lars Stindl replaced the injured Alassane Plea.
Weigl (Benfica Lisbon) and Ngoumou (FC Toulouse), who were only brought in shortly before the end of the transfer deadline, only made their debuts in the final stages.
The alleged compensation for Gladbach by Stindl (86th) was whistled offside.