The Scotsman ended his management career at the close of the 2012-13 campaign following 26 glittering years at the helm of Old Trafford.
In an interview with US network PBS, the 71-year-old insisted that the likes of Lionel Messi and Cristiano Ronaldo are unlikely to be good coaches because they would not be able to understand a player who does not have the same ability as them.
"I was only an average player, could score a goal or two, that sort of thing, but I wasn't a Bobby Charlton or a Messi, or Ronaldo," said Ferguson. "There are very, very few really great players who have become great coaches."
Ferguson has also given his backing to new United boss David Moyes and insists that he has no intention of returning to management.