Darren Ferguson insists his father's retirement had been planned for some time and has nothing to do with any health problems.
Sir Alex Ferguson will take charge of his final game at Old Trafford on Sunday before addressing the crowd following the Premier League encounter with Swansea.
It promises to be an emotional day, with the Scot's 13th championship trophy also to be collected, and feelings will be heightened because of the sudden nature of his exit.
So far, the man himself has handled the situation in the same clear-sighted way his manages his team.
"He said: 'I've got to tell you, I'm doing this, this is why I'm doing it.' And that's it," Darren Ferguson told twentyfour7football.com.
"His last game on Sunday at Old Trafford could be a bit emotional because it's my dad, it is what it is, no one will ever replace him. But he's ready to go."
Most assume the decision has something to do with the 71-year-old's health given he has always said that would be the determining factor in any decision to quit and it was confirmed last week he would have a hip operation in the summer.
However, Darren Ferguson is adamant that is not the case.
"There's no problem with his health, contrary to what some people are saying," he said.
"He's got a small hip operation but there's no difference to most 71-year-olds. It's not a health decision.
"Basically he feels he's gone out at the right time, he's left the club in a fantastic position and they've hired a very good manager to replace him."
That manager is, of course, David Moyes.
The Everton boss is going to see out the season on Merseyside and made it clear he did not wish to speak about United at a press conference to preview his own club's encounter with West Ham on Sunday.
However, as has been demanded of all other top flight bosses over the past 48 hours, Moyes was asked what he felt about Ferguson's exit, which, despite the obvious personal interest, he insists caught him by surprise.
"I don't think anyone thought the day would come when Sir Alex Ferguson retired," he said.
"We all thought he was superhuman.
"I didn't know anything about it. But I do know he will be sorely missed. The respect he is held in is beyond any real words.
"He has always been someone I have admired, then started to compete against. That was daunting enough.
"Everyone has great admiration for him. Any words I say won't do it justice because of what the man has done."
By next August, Moyes will be doing his job, coaching a team from a dug-out facing the stand that bears Ferguson's name, knowing outside there is a statue that stands in acknowledgement of the incredible number of trophies he has won.
Yet skipper Nemanja Vidic feels the transition will work out just fine.
"I am looking forward to working with David and I believe I will have the same success I had with Sir Alex," Vidic told www.manutd.com
"David and Sir Alex share some similarities - they are very passionate, they are both winners and you can see the way they approach the games and how they run things."
It has been suggested Moyes will work his new charges hard in training but that merely ties in with the regime that is about to reach its glorious end.
"David Moyes did a great job with Everton," said Vidic.
"He is the man who gets his players to work hard and show discipline.
"He did that well with Everton because in the last few years they've been successful in getting into the top six."
Sir Alex Ferguson's last Old Trafford team selection is awaited with interest.
He has been saying for some time now he hoped to have Paul Scholes available, which would mean the pair could say goodbye together given the 38-year-old is expected to retire at the end of the season.
Wayne Rooney may also be involved despite asking to leave for a second time a fortnight ago.