Lorenzo Insigne sought and found revenge for his bizarre exclusion from Gian Piero Ventura's team during Italy's World Cup playoff defeat, as he and Piotr Zielinski defeated AC Milan and gave Napoli a well-deserved - despite a late goal by Alessio Romagnoli.
The Partenopei have now a four-point lead over Juventus, while things have worsened for the Milan outfit, who looked lost and strategically weak, as Napoli dominated the game.
Insigne's stunning goal broke the deadlock for the home side, despite being at the centre of controversies. The Italian's shot was initially ruled out for offside and only later, thanks to the Video Assistant Referee's intervention, was it formally given.
An issue regarding the moment when the whistle was blown and the time of the VAR's decision still raises questions.
The home side played some impressive and entertaining football throughout a game in which they dominated with precision and style, while Milan had few chances to get out of their own half.
The first opportunity came for Napoli in the opening fifteen minutes, when Insigne - who was looking for redemption after a few poor performances - crossed the ball towards the far post. He found Callejon, whose header, however, was pushed away by Donnarumma.
Milan stoically resisted Napoli’s pressing and patiently waited to find their chance to fight back. The away side went close to breaking the deadlock with Suso, whose usually lethal left foot was stopped by Reina but could have been dangerous.
Napoli caught the Rossoneri unprepared again when Dries Mertens provided Allan with a perfect assist, but the shot was too weak and central to beat Donnarumma.
Gianluigi Buffon's successor was called to action a few minutes later, when the Partenopei threatened to score with Hamsik - still one goal shy of Maradona's record - whose shot was again too central.
The half-hour mark saw the San Paolo crowd fire up as Napoli took the lead with the controversial strike. Insigne picked up the ball from Jorginho, beat the defence with pace and shot a stunner from the verge of the box.
The referee initially declared it invalid due to Insigne’s offside, but the VAR forced him to consider it rightful. Insigne loves scoring against AC Milan, and Saturday's effort marks his sixth agains the Rossoneri.
As the teams returned to the pitch for the second half, Mertens attempted to steal the attention from Insigne with a top class efforts on the Milan goal, but Donnarumma once again tipped it over.
On the 70th minute, the newly entered Zielinski (who came on for Hamsik) doubled Napoli's lead and all but put an end to Milan's hopes to earn a point from the contest.
Mertens caught him alone on the left-hand side of the box, and served a beautiful assist for the Polish midfielder to thump home with perfect calibration.
Milan made sporadic efforts to make up for their defensive mistakes, but the difference between their's and Napoli's style of play was gigantic. However, the Rossoneri eventually scored a consolation strike, deep into stoppage time when a stunning volley from Romagnoli caught Pepe Reina off gaurd.
Napoli keep their position at the top of the table, while AC Milan - whose start to the Serie A season has so far been more troubled - needed stability, confidence and to win against a big team for the first time.
There is no doubt that Vicenzo Montella's role at Milan will be assessed in the aftermath of the match.
#ACMilan XI: Donnarumma; Musacchio, Bonucci, Romagnoli; Borini, Kessie, Locatelli, Montolivo, Bonaventura; Suso, Kalinic— AC Milan (@acmilan) November 18, 2017
Subs | Panchina: Donnarumma A., Storari, Abate, Antonelli, Rodriguez, Zapata, Biglia, Gabbia, Mauri, Cutrone, André Silva#NapoliMilan pic.twitter.com/YvEhOMkyAz