"I'm not interested in managing again, getting myself worked up," Ferguson said. "United are in good hands. David will be fine. He's a good manager."
The 71-year-old added Roman Abramovich wanted him to take charge at Chelsea when he bought the club in 2003.
"They used an agent to approach me when Abramovich first took over," he said. "And I said, 'No chance'."
The day Sir Alex resigned
Ferguson, who spent more than 26 years as Manchester United manager, stepped down after securing his 13th Premier League title, also winning two Champions League crowns, a Cup Winners' Cup, five FA Cups and four League Cups during his time in charge.
He still attends United matches at Old Trafford in his capacity as a director but is too happy with his current lifestyle to contemplate any change.
In an hour-long interview with US television network PBS, Ferguson said: "I made my decision. The timing was perfect. There is no way back for me now. I've got a new life.
"I want to go to the Kentucky Derby and the US Masters, the Melbourne Cup. I want to visit vineyards in Tuscany and France."
But Ferguson praised the form of Wayne Rooney, whom he left out in the latter stages of his tenure
amid transfer rumours,
and reiterated his claim the England striker had asked to leave United, which the player's camp always denied.
Questioned about the secrets of his managerial success, Ferguson added: "Never hold a grudge, it's very important."
And asked what he used to say to his players, he responded: "I always say to them at half-time: 'The last 15 minutes - throw the kitchen sink.'"
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