The Germany midfielder has announced he will retire after the Euros.
Casillas said at a Padel event: "He has been a fantastic player. He arrived very quietly, without making any noise. Nothing to do with the name he now has worldwide. He has won the hearts of all Madrid fans and has been a very important player for the entity.
Advertisement
Advertisement
"He could have continued playing football perfectly. Every Wednesday or Sunday he plays and it makes you happy. It's a very thoughtful decision and I suppose he and his family will opt for the best.
"Cristiano has left, Ramos has left, Casillas has left, Ral has left... and in the end Real Madrid always continues on the path."