Jose Mourinho has ended years of speculation by confirming that he agreed to take charge of Manchester United following Sir Alex Ferguson's retirement in 2013 — only to reverse his decision and return to Chelsea instead.

The revelation comes from a new Netflix documentary series charting Mourinho's career. Now 63 and back at Real Madrid for a second spell, he recalled the moment he committed to succeeding the legendary United manager.

"When I left Real Madrid, I signed to go to Manchester United after Sir Alex," Mourinho said in the documentary.

Ferguson corroborated the account, confirming that his chosen successor had accepted the role before a dramatic change of heart. "He was offered the job, yes," Ferguson said. "I sat him down and explained the situation. As far as I was concerned, he was accepting. And then, within hours, it changed."

A phone call, tears, and a change of heart

What changed was Mourinho's sense of obligation to Chelsea, where he had won back-to-back Premier League titles in 2005 and 2006. According to Ferguson, Mourinho rang him in distress that same night.

"One night, he phoned me and he was crying and he says, 'Alex, I can't take it. I've given my word to Chelsea and I'm not going to break my word'," Ferguson recalled. "The reason he gave to me, I could understand, but I was disappointed."

Mourinho described the offer as deeply flattering given "Manchester United has an incredible appeal," but said his loyalty to Chelsea ultimately proved stronger than the pull of Old Trafford. "For me to lose the chance to be the coach to succeed Sir Alex Ferguson was dramatic, but I don't regret it because it was a decision that I made with my heart," he said.

Returning to Stamford Bridge in 2013, Mourinho won a third Premier League title along with the League Cup. He later got a second opportunity at United in May 2016, replacing Louis van Gaal, and delivered the League Cup and UEFA Europa League before being sacked in December 2018.

The Casillas rift that shook Real Madrid

The documentary also revisits Mourinho's turbulent first stint at Real Madrid, during which his treatment of club captain Iker Casillas fractured the dressing room. Casillas, who made 725 appearances across 25 years at Real and won three UEFA Champions League titles, spent much of the 2012-13 season on the bench.

"The relationship Jose and I had was very cold," Casillas said. "In those years, I really think it was taken to a limit where in the end, the rope broke."

Former Real midfielder Sami Khedira described the fallout as damaging for the entire squad. "Iker is a Real Madrid legend, loved by every Real Madrid supporter. He benched him, doesn't speak to him, spoke bad about him in the media, so then this locker room was a nightmare, honestly," Khedira said. "After that, the relationship between Jose and many, many players was broken — like Cristiano [Ronaldo] and the Spanish guys, Casillas, Sergio Ramos."

Mourinho was unrepentant, insisting Casillas had displayed a poor attitude from their first exchanges and accusing him of repeatedly seeking special treatment. "In a short period of time, I realised they're spoilt," Mourinho said.

Rivalry with Abramovich and a cherished act of revenge

Mourinho also addressed his complicated relationship with former Chelsea owner Roman Abramovich, who hired and then dismissed him twice. He revealed that he had never wanted to sign Andriy Shevchenko — who cost approximately £30 million in May 2006 and managed only nine league goals in 48 appearances — and that his preferred target had been Samuel Eto'o.

After his 2007 sacking, Mourinho savoured what he called revenge when his Inter Milan side eliminated Chelsea 2-1 at Stamford Bridge in the UEFA Champions League round of 16 in February 2010, en route to winning the title.

"Honestly, I was playing against Roman that game," Mourinho said. "I go home happy and he goes home upset. Football belongs to the players, belongs to the coaches, belongs to the fans. Football will always belong to us."