But the 20-year-old had already agreed a five-year deal with Parma.
Monk, 32, said: "Fabio is a great lad and talent and it was bitterly disappointing that we couldn't keep hold of him. He played a major part in our run-in and will go down in the history of the club.
"It was hard to leave him in London but I'd like to thank him for his contribution.
"I know he had sorted out the Parma deal before he knew what was going on.
"But I'm sure if he knew what we would achieve, it would have made him think twice."