The arrivals of Denzel Dumfries and Ibrahima Konaté already reflected that approach, both seasoned internationals accustomed to operating at the highest level. But no deal defines Mourinho's new project quite like the agreement to sign Bernardo Silva.
The Portugal international is not arriving purely to provide football. He is arriving to provide personality.
At 31, Bernardo Silva will move to the Santiago Bernabéu after nine years competing at the top level, having become one of Manchester City's great leaders. It was no accident that Pep Guardiola treated him as indispensable for years, nor that he eventually inherited the captaincy of one of European football's most competitive squads.
Real Madrid gain more than a versatile talent capable of playing in several positions. They gain an authoritative voice in the dressing room, a detail that matters given what has unfolded at the club over the past season.
Madrid's squad contains a generation of young players the club believes is destined to define an era, among them Jude Bellingham, Arda Güler, Endrick, Aurélien Tchouaméni and Dean Huijsen. They represent the present and future of the club.
But Mourinho believes great teams need figures capable of transmitting experience, managing pressure and raising daily standards. Since the departures of Toni Kroos, Nacho Fernández, Luka Modrić and Joselu, the club has lacked players willing to raise their voice.
Bernardo Silva's arrival recalls other deals that initially raised doubts because of the age of those involved, before becoming clear successes. David Alaba arrived at the Bernabéu at 29 having won everything with Bayern Munich, and proved key during Madrid's run of Champions League comebacks.
Antonio Rüdiger followed a similar path, also arriving at 29 and becoming a leader and a Champions League hero, his penalty at the Etihad Stadium among the enduring images of that campaign.
That is what Mourinho wants: players with personality.
Alaba became a dressing room reference from his first day at the club. His personality, experience and willingness to take responsibility mattered as much as his performances on the pitch, even as injuries limited him from his second season onwards.
Rüdiger followed the same path with intensity, a competitive character and a winning mentality that quickly connected with supporters.
Bernardo Silva, with his own qualities, fits perfectly into that lineage. More than a midfielder or a winger, Real Madrid are bringing in a captain.
The move is also a significant blow to Atlético Madrid and Barcelona, both of whom had been linked with the Portugal international before talks with Madrid progressed rapidly. Bernardo Silva will arrive on a free transfer after his contract at the Etihad Stadium expired, closing the book on one of the defining careers of Manchester City's most successful era and opening a new chapter under a manager who has long admired him.