But while Carlo Ancelotti, like Jose Mourinho before him, has leaned toward Diego Lopez—only handing San Iker the gloves for the Champions League so far—there are others who still appreciate Spain's No. 1.
Not just Real Madrid fans, either, who have have fallen in love with the keeper during his long and successful career at the Bernabeu.
On Saturday, some Barcelona fans unveiled a banner in homage to Casillas.
"Whatever the say you are the best goalkeeper in history," it read. "You are my idol, my inspiration and it would dream for me to get your shirt—or your gloves!"
Barça supporter at Camp Nou with a message to Casillas.. (next tweet for translation) pic.twitter.com/bmlYuESCmc— Alexandra Jonson (@AlexandraJonson) October 26, 2013
Casillas' quandary is not new.
As long ago as August, former goalkeeper Santiago Canizares said that he saw no reason why rumours that he may replace Victor Valdes couldn't materialise.
"[At Barcelona] he would get the recognition he deserves," said the former Madrid and Valencia stopper, via goal.com.
Madrid won't want to be too quick to flog Casillas, though. It could come back to bite them big time in the future.
Goalkeepers traditionally can play much later into their 30s than outfield players.
Edwin van der Sar was in his 40s by the time he retired, Brad Friedel, now into his 40s as well, has only recently been knocked out of the Tottenham side, while Gigi Buffon (35) and Morgan de Sanctis (36) are still regulars in Serie A.
Iker Casillas, at 32, is of a similar profile to Valdes (31), Pepe Reina (31), Petr Cech (31) and Roman Weidenfeller (33)—hardly goalkeepers associated with being on the decline.
One problem he does have is that Diego Lopez in that same age group.
The former Villarreal and Sevilla 'keeper was born in 1981, like Casillas, but slightly later in the year—he'll turn 32 in November.
But is Lopez really, all of a sudden, better than Iker?
Luis Aragones and Vicente del Bosque have not only both preferred Casillas as their No. 1, but neither have seen fit to utilise Lopez for La Roja.
Del Bosque did call him up a couple of times—he featured for half an hour in a 3-2 friendly win over Macedonia—but he's never been considered a genuine candidate to start.
Admittedly, it's difficult for Ancelotti to drop Lopez now. He's shown faith in him and has been rewarded with some good performances.
Ultimately, it should eventually prove the kick up the backside Casillas needs to regain his form—if you buy into the reports he'd become complacent, taking his place in the Madrid goal for granted, via The Guardian.
Madrid would be mad to let another club reap the rewards from that.