"Eight-and-a-half years of big performances, not big words – Danke, Yann!" read the banner on the Nordkurve, the home of Borussia Mönchengladbach's hardcore supporters.
Not every departure from Borussia Park prompts such warm words – just ask former Gladbach head coach Marco Rose or sporting director Max Eberl, both of whom were the target of furious criticism recently after leaving the club and ending up, via different routes, at RB Leipzig.
But no such fury was aimed at Yann Sommer upon his return to his old stomping ground in the colors of Bayern Munich. The 34-year-old Swiss goalkeeper made 335 appearances in almost a decade between the posts for the Foals, including 20 in the Champions League, earning him legendary status among the Gladbach faithful.
"It was really nice and it's not to be taken for granted," he said. "We had eight-and-a-half great years together so it was nice to say goodbye like that. A huge thanks to all the fans, even if I would obviously have preferred to win here."
Indeed, Sommer's former teammates were much less welcoming, taking advantage of an early Dayot Upamecano red card and eventually running out 3-2 winners over Bayern to throw the title race wide open.
Gladbach captain Lars Stindl fired his team ahead just moments after the red card and, after Eric-Maxim Choupo-Moting had drawn Bayern level at the break, Jonas Hofmann and Marcus Thuram secured the points in the second half, despite a late scare after Mathys Tel's late consolation.
Julian Nagelsmann furious
For Julian Nagelsmann, however, Upamecano's dismissal for a last-man foul on Alassane Plea remained the turning point, as he made clear at full-time when he stormed "raging and screaming" down the tunnel, according to reporters in the mixed zone.
"It's an absolute joke, is he kidding me?” he was overheard shouting, referring seemingly to referee Tobias Welz. "My God, what a soft bunch."
Upamecano had been adjudged to have knocked Plea off balance on the edge of the box with his compatriot clean through on goal, but Nagelsmann saw things differently, arguing that the contact was negligible.
"You have to be 100% it's a clear foul before showing a red like that," he told Sky. "In my eyes, there's a minimal touch on the shoulder but he doesn't pull him. Anyone who has played football knows that Plea will be waiting for the contact there but he doesn't get it. You can see that clearly on the replays: Plea doesn't move an inch. He falls due to his loss of balance."
Despite his disagreement with the decision itself, Nagelsmann insisted the real reason for his anger was the failure of Welz to admit a mistake.
"You can make any decision, that's fine," he said. "Referees are human, we all make mistakes, even when they check it eight times, which they clearly didn't do here. But then you can also say afterwards: 'Yes ok, maybe that was harsh.'
"Because no-one can tell me that was a red, even at that speed, because he doesn't touch him enough. It simply wasn't a red."
Thomas Müller the victim
But the decision stood and, while Stindl's subsequent free-kick was well saved by Sommer, the Gladbach captain was unmarked moments later to fire home from the resulting corner, taken short by Hofmann.
It was Stindl's eighth goal or assist against Bayern in the Bundesliga, while Hofmann's assist plus his later strike put him on ten in that category. Only Borussia Dortmund's Marco Reus has been involved in more goals against the perennial champions, with 11.
Bayern were on the back foot and Nagelsmann reacted, sacrificing talisman Thomas Müller for Joao Cancelo for more stability in midfield.
"It was a lousy decision to have to make," he said. "But we had to decide quickly what to do: we needed as much pace as possible [on the counter-attack] and we needed Choupo-Moting up front for set pieces. There were lots of factors, it didn't necessarily have anything to do with Thomas. He knows we had to make a decision, even if it's a lousy one."
The nature of Bayern's equalizer proved Nagelsmann right, with Alphonso Davies bursting down the left with blistering speed and crossing for a well-positioned Choupo-Moting to stroke home.
Opportunity for Union and Dortmund
But Gladbach's advantage in numbers eventually told as Hofmann and Thuram put them in the driving seat, extending their unbeaten run at home to Bayern to four games and throwing the Bundesliga title race wide open as Union Berlin and Dortmund capitalised to move level on points with the league leaders.
Nagelsmann, Sommer and co have a real job on their hands.