The 24-year-old is poised to secure a move to Roberto Mancini's side after growing frustrated with a lack of first-team opportunities at Camp Nou.
And Montoya admits he was saddened to learn from head coach Luis Enrique that he was not part of his plans after Dani Alves extended his contract and Aleix Vidal joined from Sevilla.
"I'm sad. Luis Enrique told me he didn't count on me," he was quoted as saying by Mundo Deportivo."I wanted to go in January but they wouldn't let me because of the sanction on transfers.
"It was very clear to me I had to go when they renewed Alves and signed Aleix Vidal."
Despite harboring a desire for greater playing time for much of the past year, Montoya admits he remains hopeful of establishing himself at Camp Nou in future.
"It's like an assignment for two years. I hope to return," he added.