The docuseries, which traces Mourinho's first spell at Real Madrid between 2010 and 2013, revisits his fractured relationship with then-captain Casillas from its earliest days. Mourinho recalled his first three conversations with the goalkeeper leaving a clear impression on him.
"The first thing he told me was: 'I've come to ask for more holidays for the national team players.' The second time he asked me to push training back an hour because there was a lot of traffic in Madrid at the time I wanted to start.
"The third time he told me they didn't want to go to the hotel, that they preferred to meet on matchday and go straight to the stadium," Mourinho said. "It didn't take me long to realise they were spoiled."
One flashpoint came when Casillas phoned Barcelona's Xavi to try to ease tension between Real Madrid and Barcelona players away on international duty with Spain, a call Mourinho saw as a betrayal of the rivalry he was trying to instil.
"This is a Barcelona-Real Madrid game. When you go to the national team you can kiss each other, but not now. This is war," Mourinho said. "There are things I don't accept and never will. When someone doesn't respect me, it becomes a problem."
Casillas defended the call in the documentary, explaining the position it had put him in as captain of both Real Madrid and Spain.
"That situation was difficult, because you were captain of Real Madrid and captain of the Spanish national team. You were up against team-mates who were your enemies on the football pitch, but then your team-mates with the national team," he said. "I didn't like seeing that, and I told the manager."
Khedira, now part of Mourinho's coaching staff during his second spell at the club, described how the fallout poisoned the dressing room.
"Iker was a Real Madrid legend, loved by the fans. He benched him and stopped speaking to him, spoke badly about him in the media... the dressing room became hell," Khedira said, adding that the rift did not stay contained to Casillas alone. "After that, the relationship between José and many players broke down, players like Cristiano Ronaldo and the Spanish contingent. Those players were hugely important to the atmosphere, and it was poisoned."
The documentary also revisits the mole hunt that consumed the dressing room after lineups and tactical information began leaking to the press. Casillas recalled Mourinho's fury at the time.
"He lost it. He called us all in, said all sorts to us, said we were all to blame for everything," Casillas said.
Rui Faria, Mourinho's then-assistant, said the coaching staff were fairly confident who was responsible, even without proof: "We knew who the mole was, we were almost sure. You can't prove it, but you're almost certain of how these things work."
Elsewhere in the documentary, Mourinho reflects on the tactical side of that Real Madrid side, insisting his job was never to teach a squad already stacked with world-class talent how to play football.
"On that Real Madrid team, I had very, very little to teach any of them. I couldn't teach Sergio Ramos how to head a ball. I couldn't teach Cristiano how to score a goal," he said.
Marcelo recalled just how detailed the coach's process was in training.
"He explained everything to us, every detail. And in the end, when we got to the match after the training sessions we'd done, everything was exactly as he'd said it would be," he said.
Khedira, describing the demands of playing under Mourinho, put it more bluntly: "You're like his brain out on the pitch and you have to follow him 100 per cent. If you don't... he'll kill you."
Mourinho summed up his own philosophy simply: "If they think the way I think, life will be easier for them."
By 2013, though, that philosophy had exhausted both sides.
"I think the players had had enough of me as a leader, and I'd had enough of them too. I was fed up with the players and the press," Mourinho admitted, recalling the message then-president Florentino Pérez gave him on his way out: "Now comes the easy part, because we're going up and they, Barcelona, are going down."
Looking back, Mourinho said simply: "I wanted to leave. I felt it was over."
Mourinho is now back in charge at the Bernabéu for a second spell, working alongside Khedira as part of his coaching staff and facing a very different dressing room. The demands, by his own account, remain unchanged.