The 22-year-old Brazilian-Italian completed his transfer on a co-ownership, signing a contract until June 2018.
"He is a professional, so he knows his career can take him from one club to another. Now he is at Napoli, he arrives with a real desire to do well.
"We were struck by their plans, which impressed both me and the player. He wants to do well in a club with a great tradition behind it."
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