The Mexico international returned to Spain with Betis in August from PSV Eindhoven.
On Madrid, Guardado said: "Yes, they made an offer, to go to Castilla. They were looking for the successor of Roberto Carlos at that time and yes, they looked for me to go to Castilla for six months and see my evolution, and if I could make the leap to the first team.
"But then, I had played a World Cup and my team did not think I should go to an affiliate, even if it was Real Madrid. And they signed the same year Marcelo, and see how he has progressed."