"Cesc has become a star at Arsenal - he is someone who is maturing very quickly," Casillas told the Mirror.
"Before he had other players around him like Thierry Henry who were bigger names than him but now he is the man who has to take the leadership role.
"He has got a great deal of talent and a bright future ahead of him. If he ever decided to come back to Spain, there would be a queue of clubs wanting to sign him. Now he also has to take the same responsibility with the national team and be the main man."