Rincon's scouts spotted Ronaldo at a youth tournament in 2002 and confirms they lodged a bid for the now Juventus star with Sporting.
He recalled to El Desmarque: "It was very simple. We had to get players before the big clubs, so I forced my team to visit tournaments in Europe, America or South Africa."
Ronaldo was spotted at one such tournament and after a quick assessment, Rincon made his move, offering €1.5m for the teen.
"He was what he is now, but as a young man. A player with a very important physical power, with a spectacular strike of the ball, intuitive and with technique," said Rincon.
Malaga offered €1.5m to Sporting, but agent Jorge Mendes asked for €3.5m.
"We could not move on because we could not reach that amount," added Rincon.
Just months later, United were buying Ronaldo for €18m.