Jürgen Klopp had called on the fans to make it a "typical BVB evening". They should, he said, leave any ill feeling about Mario Götze's imminent treachery at home, and get fully behind their team.
And so they did. There was barely a solitary jeer for Götze all game, the temporarily seated "Yellow Wall" was bouncing as it always does, and BVB were making an evening of it. Except it wasn't the night of BVB. It was the night of Robert Lewandowski.
Rarely has a Polish player been able to make gasps ring so audibly around the continent as Lewandowski could last night. Rarely has a player's growing reputation been so emphatically justified in the space on 90 minutes. Lewandowski not only scored four goals against Real Madrid, he also showcased every aspect of the quality which has made him the celebrated player he is in Germany.
Here was the gentlest of touches and exquisite positioning to nudge the ball past Diego López for the opener. There was the intricate skill combined with the ferocious force of his finish for the third goal. And everywhere was his refined link up play,the incredible one-twos with Götze, the intuitive runs, all contributing so much more to his side's attacking flair than the likes of Mario Gómez or Stefan Kiessling ever do for their respective teams.
On English television, they gushed as if they had just discovered a 19-year-old nobody. Jamie Redknapp went as far as to assert that a lot of major teams in Europe would now be after Lewandowski. A bold claim to make about a man of 24, who is leading scorer in the Bundesliga and had just single handedly destroyed Real Madrid.
Any club looking to join the race for Lewandowski's signature at this late stage would be arriving only to watch the lap of honour. For if reports are to be believed, the Dortmund striker is already on his way to Munich.
It is a rumour which has been floating around the press since the dawning of the new year. At first a laughable notion, the idea of Lewandowski wearing a Bayern shirt next season is hurtling towards becoming a reality. According to Der Spiegel, Bayern made an offer of €25m as early as last Saturday, which Dortmund initially rebuffed in order to offer the striker a new contract. He turned it down.
That rejection was not entirely surprising. It was months ago now that Spiegel first reported that Lewandowski had agreed terms with Bayern for a summer move. His agent, meanwhile, told Bild today that "We have agreed terms with one club, and we plan to move this summer."
He added: "There is a very interesting offer for Robert which fulfils entirely the demands set by Dortmund and also the demands of Robert.
"Dortmund have assured us that Robert can move at the end of the season under these conditions.
"We stick to agreements and now it's up to the clubs to sort things out."
There is a general acceptance in Dortmund that Lewandowski will leave. This is his third year at BVB, and in his entire professional career, he has never been at one club for longer than three seasons. And while Hans Joachim Watzke has already asserted that he wants Lewandowski to stay for one more season, "regardless of money", it will take a lot to dissuade the Pole from succumbing to the Guardiola effect.
As for Bayern, on the face of it, it looks like they are now buying out of spite. As with Götze, Lewandowski will not fill a position in which they have any shortage of quality. But as he showed last night, the Pole is a far more complete player than Mario Gómez or even the excellent Mario Mandžukić. His combination play is more appropriate for the Guardiola system, and if, as rumours suggest, both Gómez and Claudio Pizarro are to leave this summer, Bayern will need an extra striker.
The deal is not done, and Dortmund will fight to the last to cling onto their star for twelve more months. The problem is, that Bayern have once again eclipsed them in terms of attractiveness. Two years ago, Lewandowski told the press that "I'm playing for the German Champions. Why would I go to Bayern?" Now Bayern have recovered that particular crown from Westphalia, he may well invert the sentiment.