The Blancos chief has hinted the goalkeeper will remain at the club and refused to hit out at Gerardo Martino for criticising the record sum spent on Gareth Bale
Los Blancos have started the season with Diego Lopez as first choice goalkeeper, just like he was in the second half of the last campaign, but Perez cast doubt on the skipper being shipped off in the winter.
"It'll be difficult for him to leave in [the next transfer window]," the 66-year-old told Cadena SER. "Mou's decision on dropping Casillas was made for sporting reasons. He gave him a little warning and then after that it was because he was injured.”
The Santiago Bernabeu chief refused to hit back at new Barcelona boss Gerardo Martino for criticising Madrid's €100 million purchase of Gareth Bale, suggesting that the Argentine is not used to the big-spending culture in Spain.
"Martino is new to his post and he doesn’t know very well how signings work here," he added. "It's easy to agitate public opinion."
Madrid's brought in Carlo Ancelotti to replace Jose Mourinho over the summer and Perez revealed the Italian had to be prised away from Paris Saint-Germain with a contract nearly identical to that of the departing Portuguese.
"We paid PSG €7 million for him," he continued. "We paid one half and he paid the other. He earns more or less the same as Mourinho."
Karim Benzema has received his fair share of criticism from Madrid fans since the start of the new season but Perez believes that supporters are only trying their best to get the best out of the France striker.
He added: "I think the crowd whistle Benzema to motivate him. I've even heard fans whistle [Real Madrid legend Alfredo] Di Stefano."