The story of Hansi Flick and José Mourinho didn't begin with the build-up to another Clásico. Its roots stretch back years, to when the German was working as Joachim Löw's assistant with the national team. On a trip to Madrid, Flick met the Portuguese coach for the first time, an occasion that left an impression he still remembers today.
Flick revealed details of that first meeting ahead of the showdown, stressing how highly he rates Mourinho and pointing out that plenty of German players who worked under the Portuguese speak of him with admiration, according to Spanish newspaper "Mundo Deportivo".
Speaking at the press conference before the Clásico, the Barcelona coach said: "I visited him, and every German player who met him praised him greatly. He is a wonderful colleague and a special companion, and I hold him in great respect."
That visit goes back to the 2011-2012 season, when Mourinho was in charge of a Real Madrid side containing two of Germany's most prominent players, Mesut Özil and Sami Khedira.
Löw made more than one trip to the Spanish capital during that period, keeping tabs on his players plying their trade abroad and running the rule over some of the biggest stars in European football.
At the end of 2011, Löw took in the Clásico between Real Madrid and Barcelona at the Santiago Bernabéu, a game that ended in a 3-1 win for the Catalans.
Months later he was back in Madrid, this time with Flick alongside him, to watch the clash with Olympique Lyon and grab the chance to meet Mourinho and talk over the progress of Özil and Khedira at the Bernabéu.
Real Madrid dumped the French side out of the Champions League quarter-final that night, and afterwards Löw shared his thoughts on the two German internationals, insisting their move to the Spanish club had been a crucial step in their careers.
Löw said: "We were in Madrid, and we watched the Olympique Lyon match, and we spoke with Mourinho, who expressed his great admiration for Özil and Khedira. Both of them took a big step by moving to Real Madrid, and that step was the right one for them."
He went on to praise Özil's qualities: "He has always been a player skilful with the ball, and now he is also showing noticeable progress in his movement without the ball."
The trip wasn't simply about meeting Mourinho or checking in on the German internationals. It also formed part of Germany's preparations for the fixtures ahead, chief among them Euro 2012, then only a few months away.
Local media at the time reported that these journeys let the German coaching staff study their players up close, assess a number of potential rivals and get to grips with the different playing styles of Europe's major clubs.
For Flick, such experiences offered a chance to sharpen his technical and tactical know-how, particularly given the problems Germany faced against sides that preferred to sit deep and hit on the break.
Flick said at the time: "These days, most rivals resort to defending and waiting for counter-attacks, which means we need to find new solutions."
Germany had gone out of the 2010 World Cup semi-final to Spain, before their title hopes rose again at Euro 2012. Once more they ran into Italy, beaten in the semi-final after Mario Balotelli struck both goals.
Redemption arrived in 2014. Germany lifted the World Cup in Brazil, seeing off Argentina 1-0 in the final to claim the fourth world title in their history.
Between those landmarks, the Madrid visit remains one of the memories Flick looks back on fondly when the subject of Mourinho comes up. He still holds the Portuguese in high regard, despite the gulf in their coaching journeys and the contrasting experiences each has lived through over the years.
On the touchline, though, the two have crossed swords only once. December 2019 brought them together when Flick was in charge of Bayern Munich and Mourinho was managing Tottenham. The Champions League group-stage tie ended 3-1 to the German side, handing Flick the edge over his Portuguese counterpart.
Years on, the story picks up again with another meeting looming, this time wrapped in the atmosphere of the Clásico. Here the stakes run deeper than points, a fresh test for two coaches tied together by old memories and mutual respect.
Between a visit to Madrid more than a decade ago and that Champions League meeting, Flick and Mourinho are ready to write a new chapter. The fans wait to see the tactical ideas each will bring, in a game that rewards only the smallest details and the nerve to settle the biggest occasions.