Borussia Dortmund's 1-0 victory over Bayern Munich at the Westfalenstadion on Saturday meant three points against their biggest rivals in the first Klassiker of the league campaign.
Pierre-Emerick Aubameyang's 11th-minute strike was enough to decide the biggest fixture in the Bundesliga calendar - enacting revenge on Bayern for their German Super Cup victory against BVB at the beginning of the season.
But it wasn't just Bayern boss Carlo Ancelotti that was left disappointed after the game, but also former Bayern Munich midfielder Lothar Matthaus with defender Mats Hummels' actions off the pitch, rather than on it.
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Defeat for the current Bundesliga champions saw them slip down to second and put BVB within three points of their rivals. And, as per Goal, Matthaus has criticised Hummels' decision to go into the opposing dressing room prior to the game.
The Germany defender spent seven years at Borussia Dortmund - having initially spent a season on loan at the club from Bayern - before rejoining his boyhood club this summer.
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It is understood the 27-year-old visited his former teammates in what used to be his home dressing room, before seeing his side fall to their first defeat defeat of the season.
"I would not forbid Mats Hummels if I was the present coach, but would suggest that [takes place] after the game," Matthaus admitted.
"Before the game, the concentration should be on the game and not the old friendships."
Bayern lacking fitness
And Matthaus also feels that his former club are missing something, since Pep Guardiola's departure from the Allianz Arena in the summer, for Manchester City.
Bayern have won the title for the past four seasons, under Jupp Heynckes and Guardiola, but their title defence has not been made easy this campaign, following the fairytale for Bundesliga debutants RB Leipzig, who lead the league with 27 points.
"FC Bayern is looking for its form," said Matthaus. "[They] lack fitness, joy and self-assurance.
"Many things that made them strong last year are missing here."
But Hummels, himself, feels his side could have had a far greater chance of beating his former club, had Ancelotti's men been able to put away their chances.
Hummels rues lack of ruthlessness
"We did not score the goal at the end of the day, in a game that we could have gone differently, with a better, more effective use of our chances, either through a shot or the last pass." said Hummels.
"That's not the case in the highlights, but it's a great opportunity in theory."
Victory for BVB has opened up an interesting contest for the Bundesliga title, with Leipzig having now been able to establish a three point gap between themselves and the reigning champions, while Tuchel's men are closing in on Bayern, in second.
Dortmund haven't won the league since 2012 - when Jurgen Klopp helped the club win back-to-back Bundesliga titles - but Tuchel will not only have to contend with a Bayern side that has yet to hit top form, but also the surprise pace setters, Leipzig.
Will Borussia Dortmund's victory over Bayern Munich be the turning point in their season? Give your opinion in the comment box below.