The former Spain stopper returned to the Premier League in January when he arrived on a temporary basis from Italian giants AC Milan.
He said: "After the loan spell with Aston Villa, I have to go back.
“I think it will be tough. I have 1-2 years left in my career. I think my time in football will end after next year in Milan.
“You never know in the future, but as a player I won't have a chance. As a coach, who knows."