The pair worked together in the Italy Under-21 set-up and the Watford manager reckons the 22-year-old has everything to become one of the greats of the game.
He said: "You can see his talent. He's a striker who has football intelligence, physique, two feet, he's cool in front of the goalkeeper.
"I think he has everything - but you need to bring everything together.
That's what he needs to work on. I would love to see him shining that little bit more."