Grassi, who has made 13 appearances for league strugglers Atalanta this season, put pen to paper on a contract that could see the 20-year-old remain at the San Paolo until 2020.

"Napoli would like to announce that Alberto Grassi has joined the club on a permanent contract that expires in June 2020," the club said.

Napoli, who are bidding to win their first league title since Diego Maradona steered them to their second league trophy in 1990, sit top of the league with a two-point cushion on champions Juventus.

Maurizio Sarri's men host Empoli this weekend, when Juventus are away to Chievo.

Atalanta, based in Bergamo, sit in 13th place some 21 points off the pace.