The Portugal international has said that he will assess his options at Real Madrid in two years but the former manager insists that the star is far from finished
Ronaldo has scored 19 goals in 23 La Liga games thus far this season, a tally that is well below the Portuguese's ratio of more than a goal a game since arriving in the Spanish capital from Manchester United in 2009.
The 31-year-old struggled in Madrid's narrow 2-1 win over Granada at the weekend, leading to criticism in some quarters, and recently admitted that he will assess his options after another two years at Santiago Bernabeu.
Capello, though, insists that the club's record goalscorer is far from finished.
"Cristiano Ronaldo has three more years of football, easily. He will have more experience," the Italian told Spanish radio station Cadena Cope.
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"He takes care a lot of him and he can play until 34 easily. It is not easy to find a scorer like him."
And while Capello managed another Ronaldo - the Brazilian great - during one of his two stints at Madrid, the Italian admits replacing Rafael Benitez, who was sacked by the club after just six months in January, and coaching the Portugal international was never on the cards, with Zinedine Zidane instead appointed.
"I do not know what happened in the locker room [before Benitez's departure]," he said.
"I never talked with Real Madrid to replace Rafa Benitez. Zidane has charisma, international experience and can succeed."
Zidane has made a solid start to life as Madrid coach, having led the capital club to four wins in five games.