Real Madrid superstar Cristiano Ronaldo "isn't well in the head", according to his former teammate Deco, who also tried to explain the difference between the Portugal captain and Lionel Messi.
Deco, who played alongside Ronaldo for the Portuguese national team, has insisted he has never seen anyone train as hard.
"The guy isn't well in the head. I've never seen anyone train like that, it's not easy to be like that," Deco told ESPN.
The former FC Barcelona star is one of the few players to have played with both Ronaldo and Messi and gave a few insights into the two rivals.
"They're completely different," he added.
"Messi looks after his body as an athlete should, but what Cristiano does is incredible.
"He goes to insane lengths because he always wants to be the best in every way and he competes to win everything.
"It's amazing to see both players in action, but impossible to make a comparison."
Messi is currently sidelined with an injury to his knee, while Ronaldo has linked up with the Portuguese national team for the upcoming Euro 2016 qualifiers.
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