The young Argentina striker continues to defy pundits who believe he isn't good enough to lead Real's attack.
Casillas said: "I am delighted for Higuain, he deserves to be there. It is true that he still has much to do, but he will be a very important player for Real Madrid.
"When he came to Madrid people mocked him by comparing him with Ronaldo, but he was a boy of 18. Now has shown his strength, his shot, he's fast and a great person. He can be a great player."