Bookmakers have recently shortened the odds on the Scotsman's return following an inconsistent start to life at Old Trafford for David Moyes, who has witnessed his side lose three of their first six Premier League fixtures.
Ferguson, who left United at the end of last season after 26 years in charge of the club, has also stated that he no longer gets "worked up" over the North-West side's results.
"I'm not interested in managing again or getting myself worked up about Manchester United's results," Ferguson told US television network PBS. "United are in good hands with David Moyes. He will be fine. He's a good manager.
"You would be throwing your money down the drain if you put any money on me coming back as a manager. I made my decision. The timing was perfect. There is no way back for me now. I've got a new life."
Ferguson's former club are preparing for this evening's Champions League group clash against Shakhtar Donetsk.