Casillas has fallen out of favour at Real this season, losing his starting place to Diego Lopez after being first choice at the Bernabeu and for Spain for over a decade.
Manager Jose Mourinho's expected departure from Madrid in the summer could well see Casillas come back into favour but were the Portuguese to stay, further speculation would mount over the stopper's future.
And with Barca keeper Victor Valdes set to leave the Nou Camp after confirming he will not extend his contract beyond 2014, there is set to be a vacancy between the sticks for the Catalan giants.
That would open the door for the most controversial Spanish transfer since Luis Figo moved the other way 13 years ago, but Xavi does not see his Spain team-mate making the move.
He told Spanish television program The Goal: "Iker will not come to Barca.
"He's a Madrid man and would not walk away. I would welcome it but do not see it here, honestly."
He added: "I feel bad for him to see him on the bench. I think it is unfair. He does not deserve it."
Valdes' announcement in January that he would not be signing a new deal was met with some hostility in Barcelona, and Xavi was quick to jump to the defence of his long-time team-mate.
"Valdes has had the worst media treatment I've seen in my career," he said.
"Knowing Victor, who is an extraordinary man, I feel bad that he is leaving.
"He is a friend, a piece of the furniture and a guy who deserves better."