The 24-year-old striker was the subject of a healthy offer from the Toffees but his representative Silvio Pagliari says Napoli simply did not want to sell.
"Napoli didn't want to sell the player, they refused many big money offers," Pagliari told Sport Italia.
"You could say that the club believes in him. Manolo has the potential to do well.
"I'm expecting a big renewal for an important player. I presented many offers to them from England and elsewhere, but they always refused them."