The Tottenham forward has signalled his intention to join the Spanish side to Spurs chairman Daniel Levy but as it stands the north London club are refusing to sell their star man.
|1/4||Gareth Bale is 1/4 with Paddy Power to join Real Madrid
"We’re talking about a player who, frankly, is among the three or four best in Europe, and it is normal to talk about him," the 32-year-old goalkeeper told reporters.
"It’s normal that people talk about him because he has great qualities."
When asked if Real Madrid should break the world transfer record to sign the Welshman from Spurs, Casillas added: "That’s how the market is.
"All signings are controversial for better or for worse, but we are talking about a decisive and very good player.
"Before the transfer window closes I’m sure there are could be some activity."
Bale scored 21 Premier League goals last season and was the named the PFA and FWA Player of the Year as Tottenham narrowly missed out on a place in the Champions League.