"It was the first game in the new Sporting stadium. I remember it perfectly, as if it were today," Ronaldo told DAZN. "I was happy. I was going to play against one of the best teams in the world and the game was spectacular.
"I mentioned to my friends at the Sporting academy that I would play against Manchester and that I was a bit nervous. Nervousness is a part of being a football player, in big games.
"I’m always nervous because I always want to play well and do the best I can for my team and nervousness always plays a part. But when you’re nervous and focused, things usually work out better.
I was motivated, I was happy and I knew that if I played well it would generate even more interest, not only from Manchester [United], but from other clubs as well because I was being watched.
"I felt that many teams came to watch me and of course watch Sporting too. The game went really well for me.
"I try to take all big challenges as a big test. Not anymore, but when I was younger, it was always a big challenge. Obviously, with maturity, you’re able to control your emotions but I knew it was an important step in my career.
"There were a lot of clubs interested in me at the time. I always had my feet on the ground and I knew that my future would be in football, that I would be a professional footballer and my life would be around football.
"I was taking it step by step. This time it was about playing, enjoying the game, playing against Manchester [United], a great team, doing my best, trying to play an excellent game and obviously things went well.
"The before and after... I didn’t think about it. I was just thinking about the moment and enjoying the game."
Ronaldo, now with Juventus having won numerous titles with both Real Madridand Manchester United prior to his switch to Serie A, failed to hit the net against the Red Devils that day in 2003 and he suggested 100 teams would have wanted him had he scored.
"Obviously, I think you always change," he said. "I was more of a dribbler back then, I wasn’t as direct as I am now and in recent years. I was a talented dribbler and I used to like assisting. Obviously with time and experience I’ve changed and, I believe, for the better.
"To score wasn’t important, honestly. If I had scored, maybe there would have been 100 teams after me. Since I didn’t score, there were only 50 teams! I think the most important thing was to play well and help my team win. Even without a goal the interest was very high.
"I have to say, and it’s true, Manchester [United] were already interested in me before the game. The game was like the icing on the cake. I played well, I shone in the game and this aroused even more interest.
"After the game I felt I had nothing left to prove to anyone. Every club knew after that game that if they bet on me, they would win."
The Juve forward also revealed how Ferguson spoke to him in the United dressing room after the game and how that helped convince the teenager that a switch to Old Trafford was the right move.
"It was just after the game," he revealed. "I remember that the game was over. There was a Sporting director who called me over and said that Ferguson wanted to talk to me.
"I left the dressing room and went to the other dressing room with him, along with an interpreter. He showed his interest, we talked, and obviously I was very happy.
"Knowing that I was a young man and feeling that everyone wanted me on their team, that for me was an emotional moment."