كتب : Hatem Maher
Messi has been widely criticized for failing to reproduce his dazzling Barcelona displays on the country level as Argentina stuttered to reach next year's World Cup finals in South Africa.
"It's true that he plays differently with Argentina," Casillas, who plays for Barcelona's arch-rivals Real Madrid, was quoted as saying by Marca on Thursday.
"Messi is Messi and he will enjoy playing against Spain, and he will want to show that he is a great player against a very strong national team."
Argentina's technical director Carlos Bilardo, who led the country to the 1986 World Cup title as a coach, also leapt to Messi's defense.
He said that Diego Maradona, the current Argentina manager and the player who inspired Argentina to World Cup triumph 23 years ago, endured similar problems before the tournament.