The 26-year-old was just three months into a nine-month deal when the Serie A outfit announced that his deal had been terminated by mutual consent.
And the former Real Madrid keeper, who briefly replaced Iker Casillas at the Bernabeu, has now joined Gabriel Calderon's Spanish top-flight strugglers.
"The main reason I've decided to come is the feeling this club gives me," Adan said. "After a game against Real Madrid I got the feeling this was a very big club. I'm hugely motivated.''
Adan will be formally unveiled on Wednesday and could make his debut in Sunday's home match against Espanyol.
He insists he is not worried about being thrown into a relegation fight.
"I'm aware of the situation that the club is in but I had to take this step," he added,
"The important thing is to be realistic. The situation is difficult but the first thing is to give everything on the pitch.''
