Napoli hosted Sassuolo in the sixth round of the Italian Serie A.
Gattuso's players failed to convert their chances and conceded twice in the second half.
Napoli - Sassuolo 0: 2.
Goal: Locatelli, 58 (pen), Lopez, 90 + 5 Napoli: Ospina - Di Lorenzo, Coulibaly, Manolas, Hisay (Mario Rui, 70) - Bakayoko, Fabian Ruiz, Mertens (Elmaz, 70) - Politano (Zelinski, 78.
Sassuolo: Consigli - Ayhan, Ferrari, Chirikesh (Burabia, 90 + 1), Rogerio - Lopez, Locatelli, Traore (Defrel, 68) - Mulduur (Kariopoulos, 81), Raspadori (Marlon, 88), Boga (Obiang, 81).
Warnings: Manolas, Ospina - Locatelli, Burabia.