The goalkeeper says that his Real Madrid team-mate deserves all the praise and believes that his side are working towards their potential to win the treble this season
Addressing an anti-bullying event on Tuesday, the Spain international lavished praise on the Portugal international, who has scored 17 goals in 14 Liga appearances for Los Blancos this season.
"There's one player who's ahead of everyone else, who's in amazing form and who deserves all the praise," the Madrid captain enthused. "That player is Cristiano Ronaldo.
"I don't think there's any doubt about it and he shows it game after game. It's good for Madrid because our hope is that, thanks to him, in a few months' time we'll be achieving our goals for this year."
Indeed, Casillas believes that Carlo Ancelotti's men have the potential to win the treble this season.
"We're working for it," he explained. "We're training for it but we can't go crazy because even though right now people are praising us, that can take the edge off. We need to keep going as we are right now and wait for the end of the season.
"This is a young, ambitious team. Hopefully, we'll win the Champions League - we've been waiting for it for 11 years - another league and, why not, the Copa del Rey."
The 32-year-old, who has been forced to play second fiddle to Diego Lopez in La Liga this season, also spoke about the criticism with which he is forced to deal on Twitter.
"On social networks people insult me a lot," Casillas observed. "There's a lot people who call you names behind an avatar but then, in person, they're cowards. If this happens, you should go to the police, who act to block accounts."