Kaka has hailed the longevity of "incredible" former Real Madrid team-mate Cristiano Ronaldo
Ronaldo shows no signs of slowing down after helping Portugal to their first major international trophy at Euro 2016, having guided Madrid to Champions League glory in May.
The 31-year-old scored the winning penalty in the Milan showpiece against Atletico Madrid as Madrid claimed an 11th European crown, capping a stellar season for the club's all-time leading goalscorer, who netted on 51 occasions in all competitions.
And in an interview with Omnisport, Brazilian star and now Orlando City captain Kaka - who played alongside Ronaldo at the Santiago Bernabeu from 2009 to 2013 - said: "It's incredible, he shows every year that he can beat himself.
"Every year he has motivation to keep going, to keep scoring and be the best player in the world.
"Sometimes when you have won a lot of things in your career, it is normal to slow down a little bit so maybe the motivation in your mind and mentality is not easy.
"But he is so incredible like [Lionel] Messi because these guys have won everything they could and they still want to win, they still want to be the best. It's incredible."
Ronaldo - winner of 18 club trophies throughout his illustrious career - sat out Madrid's UEFA Super Cup victory over Sevilla last week as he continues his recovery from a knee injury, which cut short his participation in the Euro 2016 final in July.
The former Manchester United forward is unlikely to feature in Madrid's LaLiga opener at Real Sociedad on Sunday, though he could be fit for the visit of Celta Vigo the following week.