Casilla looks set to leave the Spanish side this summer, with the player hesitant about signing a new contract.
"At the moment there is no news about the future," Jose Alberto Salas told Calcio Mercato.
"It is still too early to say what will happen. I have no news to tell you about Milan, or Manchester United for that matter.
"If Milan were to call it would be an honour and of course we'd speak to them.
"Milan are a historic club, a great team. Everything is possible. Serie A is one of the best Leagues in the world.
"I have a very good opinion of Italy.
"At the moment we are talking only with Espanyol, but there are some differences between us.
"If there's no renewal then he may leave in the summer - that all depends on what offers we get though."
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