Fiorentina ended Inter Milan's perfect record in stunning style while AC Milan were beaten and Lazio moved up to fourth.
Juventus could only draw 1-1 at home to Frosinone in Serie A on Wednesday, as leaders Inter Milan beat Hellas Verona 1-0.
A Gonzalo Higuain-inspired Napoli ran riot against Lazio while there were also wins for Inter Milan and Fiorentina.
Summer signing Paulo Dybala netted a late penalty to earn Juventus a 1-1 draw against Chievo.
Serie A champions Juventus saw their 47-match unbeaten home league record come to an end against Udinese.
Fiorentina finished their Serie A campaign on a five-game winning streak after beating 10-man Chievo 3-0.