Clarence Seedorf suffered a Serie A defeat for the first time as AC Milan coach with Gonzalo Higuain on target twice for an impressive Napoli in a 3-1 win.
Adel Taarabt marked his Milan debut with a goal to put the Rossoneri ahead, but Gokhan Inler replied immediately.
Higuain then struck twice as Rafael Benitez's men coasted to a deserved victory which re-establishes their three-point advantage over fourth-placed Fiorentina and takes them to within three of second-placed Roma, who face Lazio in a derby on Sunday.
In spite of a 3-2 defeat to Roma in the Coppa Italia in midweek and a 3-0 loss at Atalanta last weekend, Benitez was buoyant about his side's chances of bouncing back with two wins in the coming week.
It looked like that faith was not misplaced either as Napoli took the game to their hosts, setting up camp in their half and putting Milan's wobbly defence to the test.
When Milan broke for the first time in the eighth minute they laid bare Napoli's own defensive misgivings with Taarabt allowed to advance with the ball at his feet before placing a shot beyond the reach of Pepe Reina into the bottom right-hand corner.
It was a fine way to open his account for his new club, but Milan's lead did not last long.
Napoli's reply was an equally impressive effort from Inler, whose shot from 25 yards took a deflection off Nigel De Jong to loop over Christian Abbiati.
The Milan goalkeeper could count himself fortunate still to be on the field soon after as in the 22nd minute he floored Dries Mertens after he latched onto a delightful lobbed ball over the top from Lorenzo Insigne.
Another ball over the top, this time from Jorginho, was volleyed just wide by Marek Hamsik before Insigne's persistence led to Christian Maggio hitting the post as chance after chance went begging for the hosts.
The Napoli onslaught continued into the second half with Insigne's dipping shot only just clearing the crossbar before Higuain glanced Inler's cross in to give Napoli a deserved lead in the 56th minute.
Michael Essien fired a warning for Napoli with a shot from distance and when Higuain wasted another chance to double Napoli's lead, it seemed like their could yet be another twist in the game.
Taarabt nearly provided it with a shot which Reina fumbled out with Mario Balotelli unable to slot the loose ball in while Giampaolo Pazzini went even closer to beating the Napoli custodian.
In perhaps Milan's best spell of the game, Napoli raced clear with Hamsik sending through substitute Jose Callejon, who squared for Higuain to wrap up victory with less than 10 minutes to go, much to the relief and joy of the Stadio San Paolo crowd.