Red-hot Fiorentina replaced Inter Milan as Serie A leaders by cruising to a 3-0 home victory over Atalanta on Sunday.
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.
Eder set the ball rolling as Sampdoria maintained their unbeaten start to the season with a 2-0 victory over Bologna.
Serie A champions Juventus saw their 47-match unbeaten home league record come to an end against Udinese.
Manchester United have signed Argentina international goalkeeper Sergio Romero on a three-year contract.