'R9' burst onto the scene with PSV Eindhoven in 1994 and sealed a move to Barcelona in 1996.
He'd only spend a year in Catalonia and one of the clubs earmarked for a bid were United - with discussions even taking place with his agent.
"Ronaldo's agent asked me a little while ago if I would be interested in the player," Ferguson wrote in A Will to Win per Daily Star.
"My first reaction was to wonder why Barcelona would sell such an important player after paying £13 million for him only last July.
"The agent said that there was no problem; there was a clause in his contract which allowed him to move if an offer came in above a certain sum.
"He told me I wouldn't even have to talk to the club. I could go straight to the Spanish FA.
"So then I asked him about money. I soon told him he was talking to the wrong guy, and that he should go and see the chairman and frighten the life out of him, not me!
"It transpired that the fee would be around $32 million, with a salary of $4 million a year. We are talking here about a £20 million transfer fee plus a pay packet of well over £2 million a year."
Ronaldo would instead join Inter Milan and become one of the world's most feared forwards, even winning the Ballon d'Or in 1997.
Ferguson continued: "Now I would love to see Ronaldo playing for Manchester United.
"I have a gut feeling Old Trafford would be his kind of stage. But can you really justify that kind of outlay when you are a public company? Perhaps I could steal the Crown Jewels...
"How would the rest of our players feel? And what if he did an Emerson and didn't take to life in Manchester?
"And what guarantee would we have that the same agent wouldn't be hawking him around again in six months' time?"
Injury would blight Ronaldo's career but he still managed to win the World Cup with Brazil in 2002 before joining Real Madrid.
Featured Image Credit: PA Images
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