Ryan Giggs would have succeeded Alex Ferguson as Manchester United manager if the winger had stopped playing at the age of 35 instead of continuing until he was 40, the Scotsman has said.
Ferguson, who makes the comments in the documentary 'Sir Alex Ferguson: Secrets of Success', to be screened on BBC One on October 31, also defends David Moyes' ill-fated appointment as his successor.
"If Ryan Giggs had retired six, seven years ago ... at, say, 35, quite likely I would have made him my assistant and quite likely he could have moved straight into the job with the experience of being an assistant manager to me as he is doing with Louis van Gaal at the moment," Ferguson says.
"But I would never have asked a player to quit," he added.
The film then cuts to a surprised Giggs, who made 963 appearances for United.
"He said that?... It would have been great for me personally to work under Sir Alex," the Welshman says.
Moyes was sacked after less than a full season at Old Trafford, but Ferguson insists the club did not make a mistake by hiring him.
"We did the best under the circumstances we were in," Ferguson says, adding that it was nonsense to suggest that Moyes' appointment was his decision alone.
"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... Jose (Mourinho) was going back to Chelsea, Carlo Ancelotti was going to Real Madrid, Jurgen Klopp had signed a contract with (Borussia) 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 September and I had no idea I was ever going to retire and I said to him give me a call and tell me what you're going to do. No answer.
"I don't think we made a mistake at all... We picked the right man. Unfortunately it didn't work for David."
Mourinho says in the film that Ferguson knew he was going back to Chelsea.
"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.
"He knew that for almost a season I want to leave Real Madrid and I want to come to Chelsea."