The Real Madrid captain refused to reveal who he thinks is better, describing the two players as the best.
The goalkeeper avoided having to choose either Messi or Ronaldo, though he did concede that if he had to, it would be the Portuguese, solely for the fact that he "knows him more."
In an interview with Mexican television station, Univision, Casillas said: "We are talking about the two best players in the world now and this always make for a great debate. Some think Messi, others think Ronado is better. I cannot opt for any."
Yet the Real Madrid star did eventually allude to who he rated more highly.
"If I had to choose one, it would be Cristiano, because I know him more for we play together at club level," he continued.
Casillas went on to say he believed having two great players in the world is better than having one.
"We are talking about the two best players in the world right now, and I think that if there were only one, it wouldn't be as good for football," concluded the 31-year-old.
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