In an interview with France Football, Ferguson made clear how it was Ronaldo's performance in a friendly for Sporting CP that convinced him to pursue his signature.
"I told Ronaldo to join us.
"He explained he'd have to talk with his mother about it.
"I think his mother and Jorge Mendes were impressed by the promise that such a young boy wouldn't be thrust into the first team," he intimated.
"We had a plan so that he could adapt calmly to life at the club."
On Real Madrid's interest, Ferguson revealed Mendes' influence.
"Ramon Calderon wanted to win re-election and used Ronaldo as an electoral weapon, that wasn't right," he said.
"In 2009, Florentino Perez became president and it became easier to handle the transfer with him.
"Mendes was extraordinary; he sacrificed his own financial interests for the benefit of the player's career."