Over in Leverkusen, they will tell you that it was the Bayern Munich game in September of last season that had them believing they might be onto something. Xabi Alonso's side had won their first three games when they went to Munich and drew 2-2.
"In the pre-season, you feel like, oh, we have a good team," says Simon Rolfes, Bayer Leverkusen's sporting director. "When you start the season, okay, we have a good team. Then we play in Munich. Okay, we are competitive, really at the top."
It was proof they were at least a match for the team that had won the Bundesliga 11 times in a row. As it turned out, Leverkusen were rather better than that, powering to the title and becoming the first unbeaten team in the competition's long history.
"At a certain point of the season, it was as if we had the feeling that we would not lose and that is a special feeling. Okay, we cannot do exactly what we want, but at the end we will win, you know? If we push and we push, we will score, we will score.
"That was always the mentality and self-belief of the players, that we will find a solution, we will get it, however we have to do it. And that makes it really special because it did not stop after winning the Bundesliga title. We continued to score in the last minute."
The unbeaten record has now gone but Leverkusen remain the team most likely to challenge Bayern. That knack for late goals remains. It won them the Supercup against Stuttgart with 10 players. Their winner on the opening weekend came in the 101st minute.
And while competing with Bayern financially is out of the question - Leverkusen prefer to talk of top four and measuring themselves against Leipzig - they still have Xabi Alonso and a squad that has been built with some of the savviest recruitment around.
To explain how all this happened, how Leverkusen became the envy of Europe in upsetting the odds, it takes more than Alonso. It required a recruitment rethink, one Rolfes now freely admits was rooted in the mistakes that were made along the way.
"Besides the technical, tactical and physical skills, the personality also is crucial, and if this is bad, in our opinion, we will not sign the player," he explains. "That was also a key learning from our season two years before, when we really struggled."
Alonso's predecessor Gerardo Seoane lost his job but Rolfes understood that at least some of the responsibility lay with the recruitment. "We had to take a deeper look into this project about how we analysed players, what characteristics we wanted."
Rolfes is a legend at Leverkusen, a midfielder who won 26 caps for Germany during his decade with the club as a player, but his interests are varied - technology among them. He talks excitedly about artificial intelligence. Data drives their scouting processes.
"If you do not use it, it is just a hobby. For me, it is a normal development. Technology is getting better and better. The data is more precise and you can use it in a better way. We try to find some key performance indicators that say, for us, this is important.
"We believe in our scouting department. We find players through the process and not the other way around. We do not just look at some players and say, that is a good one, let's take him. We try to have a clear process to identify the right profiles."
That is when the subjective assessment of their character kicks in. "He looks good, but what is he like mentally? We try to get as much information as possible." It is not easy to know someone inside out, he admits. "Even your wife can surprise you," he jokes.
And there is an awareness that not everyone needs to be the same. "Our goal is not to have 25 players alike. You need different characteristics. Introverts and extroverts. Leadership guys. But a player without intrinsic motivation? It is difficult to be a top star."
Rolfes is reluctant to name names when it comes to those who did not have the motivation required - the clue is that they are long gone. But he is happy to provide an example of a player who embodies the qualities Leverkusen want to see in a player.
Robert Andrich has just been rewarded with a new contract, reflecting his pivotal role in Leverkusen's success. He was almost 25 when he made his Bundesliga debut for Union Berlin. Now he is a cult hero. "Robert is for me a fantastic role model," says Rolfes.
"He has had a very special way to the top and that is what I like. A lot of top players are more or less the best in their academy, they make it really early. Robert really worked, made it step by step and then became an international player at 29. I really like this.
"He was always able to adapt to the next level. It shows that with a good mentality, with intrinsic motivation, you can achieve a lot. Sometimes, young, high-potential players have to learn this because they are so skilful they are used to being better than others."
Leverkusen's recruitment last season was remarkable, Granit Xhaka, Alex Grimaldo and Victor Boniface among those helping to transform the team. This time around, they have retained the key players and added to the group for the Champions League challenge.
"It is important to keep the core structure of the team but refresh it," explains Rolfes. "That is our idea. We signed a defender, a midfielder, an attacking player. So in each part of the squad, there is a little bit of new competition, maybe a new hierarchy."
But improving this squad is not so easy now. "The players are performing at a high level now but we did not sign them at that level. And now we are trying to add guys at their level? For sure, that is difficult. The budget did not change because we won the title."
Now, of course, there is the draw of joining the Bundesliga champions. And the lure of working with Alonso. "We could not have signed Xhaka or Grimaldo if they did not have the feeling that it was a really interesting club with an interesting head coach," he adds.
Keeping Alonso was key. "I always had a good feeling that he would stay." But Rolfes knows that it will not be forever. Part of his job is to plan for the succession. That too, he hopes, will bring more attractive candidates now that Leverkusen are proven winners.
"Each successful story is helpful for the next one. That is also the case with the players. Kai Havertz, for example. He was 17 when we counted on him and his career path helped us to sign Florian Wirtz. He played at 16. He will maybe help the next one."
Before that, the aim is to add more trophies. There is an awareness that with this group of players, under this particular coach, there is an opportunity there. "This motivates me a lot and I can feel it that it is also motivating for others to try to get the next chance."
He adds: "The challenge is different because the expectations are very high now. Some guys think maybe we can win again." A dip in performance might be only natural? "That is challenging, it is human after such a season. You really have to be careful with this."
But Rolfes is optimistic. "Some things are easier as well. Now there is confidence to say, okay, we can win a final, we can win the championship. That gives us confidence we can compete." The intrinsic motivation is there. Leverkusen are coming for Bayern again.
Watch Bayern Munich vs Bayer Leverkusen live on Sky Sports Football this Saturday; kick-off 5.30pm