Lorenzo Insigne's shot from distance has put Napoli on course to beat champions Juventus and move within two points of the Champions League places.
Gli Azzurri made a bright start at the San Paolo, with Gonzalo Higuain firing an effort over the bar before Marek Hamsik brought an early save out of Gianluigi Buffon.
The Bianconieri also went close to making a breakthrough in the opening stages as Paulo Dybala's slide-rule pass played in Simone Zaza, who was denied by ex-Liverpool keeper Pepe Reina.
It was Napoli who opened the scoring on 26 minutes when Higuain teed up Insigne and the forward steered his effort into the bottom corner of the net.
However, that would prove to be Insigne's only major contribution after he was forced off with an injury before half time.
Moments before Insigne's exit, Juve missed a chance to get back on level terms as Zaza headed Simone Padoin's cross wide of Reina's goal.
