"I won't be managing here any more than three years at the very, very most. Without question. I can assure you of that," Ferguson told the Sunday newspaper.
"The big fear about retirement is what do you do with yourself.
"What you're left with is the time when you wake up at six o'clock in the morning and you go to get out of bed and you say to yourself: "I'm finished". That's the hard part.
"You have to think about time for yourself. I think my wife deserves a bit of my time, too.
"The older you get, the more you feel guilty about it.
"My wife, Cathy, was the one who talked me out of retiring last time but she wouldn't do that now.
"I know I would find it hard to give up managing United," he added.
"I can't do it, not at the moment anyway.''