The 22-year-old could not add to his tally of 10 goals after 23 matches in his debut Serie A campaign.
Despite the absence of Senegal centre-back Kalidou Koulibaly who is recovering from an injury in the calf muscle of his right leg, Gennaro Gattuso's men were solid in defence and kept their first clean sheet in almost a month.
Fiorentina, however, had Ivory Coast's Christian Kouame in action as an 83rd-minute substitute for Franck Ribery while Morocco's Sofyan Amrabat watched on from the bench.
The victory pushed Napoli up to third in the Italian top-flight standings with 76 points after 37 matches, a point above AC Milan who host Cagliari at the San Siro Stadium later on Sunday.