José Mourinho has said that his heart was always set on returning to Chelsea and that Sir Alex Ferguson knew it would have been pointless to ask the Portuguese to be his successor at Manchester United when he retired in 2013.

Mourinho effectively issued a public challenge to Roman Abramovich to sack him after Chelsea slumped to their fourth Premier League defeat of the season on Saturday, losing 3-1 to Southampton, and the club responded by offering their manager a vote of confidence on Monday. Despite the uncertainty over his future, however, Mourinho maintains that Ferguson was aware that he could not be tempted to replace him when he left United in 2013.

“Every manager in the world looks at Man United as a huge club but I wanted to come to Chelsea and we didn’t bring that to the table because we were so open and he knows so much about myself,” Mourinho said during an interview for a new BBC documentary, Sir Alex Ferguson: Secrets of Success. “He knew that for almost a season I want to leave Real Madrid and I want to come to Chelsea.”

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United chose David Moyes instead and, although he was sacked before the end of his first season, Ferguson used the documentary to deny suggestions that he forced through the ill-fated appointment of the former Everton manager. Ferguson, who revealed that he would have made Ryan Giggs his assistant if he had retired six or seven years ago, added that choosing Moyes was not a mistake.

“When I announced my retirement, do you honestly believe that one man could decide the future of Manchester United?” Ferguson said. “That’s absolute nonsense. There was a good process. They’re a professional football club. They know what they’re doing, the Glazers, David Gill. José was going back to Chelsea, Carlo Ancelotti was going to Real Madrid, Jürgen Klopp had signed a contract with Dortmund, Louis van Gaal was staying with Holland for the World Cup.

“The other thing was I took Pep Guardiola for dinner in New York in the September and I had no idea I was ever going to retire and I said to him give me a call and tell what you’re going to do. No answer. I don’t think we made a mistake at all. I think we chose a good football man. He did a great job at Everton, 11 years there. We picked the right man. Unfortunately it didn’t work for David.

“We’d like to have spoken to many managers, believe me, because that’s the process. We’d like to have asked them what they felt about leaving a big club to go to a bigger club. To come to Manchester United. But it wasn’t there for us. I think we did the best under the circumstances we were in.”

However, Ferguson scoffed when it was put to him that it was impossible for Moyes to succeed, pointing out that United won the title in his final season. “There’s this continual thing about we left an old team and all that nonsense,” Ferguson said. “We won the league by 11 points. It’s unbelievable. The average age of my teams consistently in the 20 years when we started winning the championship was 27 to 28. Every year.”

Ferguson went on to reiterate his belief that Giggs has the potential to succeed Louis van Gaal as United’s manager one day. Giggs is currently Van Gaal’s assistant. “If Ryan Giggs had retired six or seven years ago, say he had retired at 35, quite likely I would have made him my assistant and quite likely he could have moved right into the job with the experience of being an assistant manager for me, as he’s doing and helping Louis van Gaal at the moment,” Ferguson said. “But I would never ask a player to quit.”

Giggs reacted with surprise when he was told about Ferguson’s comments. “He said that?” he said. “I obviously played until I was 40. It’s obviously a completely different job, a completely different mind-set, going from playing to coaching. It would have been great for me personally to work under Sir Alex, to see how he worked behind the scenes, because you don’t really see that as a player.”

• Sir Alex Ferguson: Secrets of Success will be on BBC1 at 10.30pm on Sunday 11 October