The now-retired 36-year-old appears to have suggested his compatriot, who has been repeatedly linked with the Liga giants, is destined to move to Camp NouSantos starlet Neymar is bound for Barcelona.
Neymar has been repeatedly linked with with the Blaugrana and Goal.com exclusively revealed last week that the 21-year-old will be heading to Catalunya in July for talks.
However, in discussing his compatriot's chances of establishing himself as a modern great, Ronaldo appears to have suggested Neymar's rumoured switch to Barca is a done deal.
"He has the potential [to become one of the world's best]," the now-retired striker is quoted as saying but Tuttosport. "But we have to assess his impact on European football when he arrives at Barcelona.
"The first year will be difficult for him, but I'm convinced that when he adapts he'll be one of the very best."
Ronaldo enjoyed a fine season at Camp Nou before leaving for Inter in 1997.