Ronaldo and Juventus will be in Lyon next week for the first-leg of their Champions League round 16 tie.
Aulas revealed to L'Equipe: "During a youth tournament in Portugal, we met Cristiano Ronaldo.
"He was 15-16 years old and he was already very strong. I tried to buy him from Sporting Lisbon, but unfortunately I couldn't.
"I am satisfied to have seen the beginning of a fantastic story. Cristiano Ronaldo is crazy and I am not surprised that at 35 he still has incredible means."