Real's Castilla have come in for criticism this season over the lack of players graduating to the first team.
But Granero argues: "What matters is how the Real Madrid youth squad has helped those that are now in the first team. Like Iker Casillas and Alvaro Arbeloa.
"And this system has also helped players like me and Juan Mata (Chelsea).
"Real Madrid is the best club in the world and to play, even if you are in the juniors, is not easy. If it was easy, the team would not be so great and not so good."