Mourinho worked as an interpreter for Bobby Robson during the Englishman’s time in charge of Barcelona, with Ronaldo among those brought onto the books at Camp Nou.
One of the most fearsome frontmen to have ever played the game starred across one memorable season in Catalunya, before going on to thrive at Inter and Real Madrid.
Mourinho considers the two-time World Cup winner to be the greatest, even when taking into account the exploits of five-time Ballon d’Or winners Messi and Cristiano Ronaldo.
“Ronaldo, El Fenomeno, Cristiano Ronaldo and Leo Messi have had longer careers, they have remained at the top every day for 15 years,” Mourinho told LiveScore.
“However, if we are talking strictly about talent and skill, nobody surpasses Ronaldo [Nazario].
“When he was at Barcelona with Bobby Robson, I realised that he was the best player I’d ever seen take to the field.
“Injuries killed a career that could have been even more incredible, but the talent that that 19-year-old boy had was something incredible.
“In 1997, Barcelona played against PSG in Rotterdam and Ronaldo’s goal, 1-0. Awesome.”
Ronaldo netted 47 times in just 49 appearances for Barcelona that season.
That would remain the most prolific campaign of his iconic career by the time the day came to hang up his boots in 2011.
The likes of Argentine superstar Messi and Portuguese forward Ronaldo have gone on to top those numbers, while breaking countless scoring records with their incredible feats.
Mourinho, though, clearly feels that a Brazilian phenomenon deserves top billing because he was untouchable at times in an era where it was harder to deliver such talismanic showings.
Ronaldo is assured of a place among the all-time greats, regardless of where he sits on that list, with his stunning CV including 352 goals at club level and 62 in 98 appearances for his country.