Match ends, Napoli 3, Milan 1.
Adel Taarabt scored on his AC Milan debut but ended up on the losing side as Napoli came from behind to win.
Taarabt, on loan from QPR, ran from inside his own half before curling a low shot into the net from 20 yards on seven minutes.
The hosts levelled four minutes later when Gokhan Inler fired a deflected 25-yard strike into the top corner.
Gonzalo Higuain headed in after the break before sealing the win from six yards late on.
AC Milan, who were unbeaten in the league under new boss Clarence Seedorf, gave debuts to Morocco midfielder Taarabt and former Chelsea defender Michael Essien.
Seedorf replaced Massimiliano Allegri last month after a poor start to their Serie A campaign.
But for much of the game it was Napoli, third in Serie A, who dominated as they look to secure a top-three finish and Champions League qualification for next season.
It was the perfect start for Taarabt though, who scored only his second goal of the season when he drove through Milan's midfield before curling a precise low finish into the net.
His previous goal this campaign came in a 2-2 League Cup draw at Burton while on loan at Fulham.
The Rossoneri were not ahead for long as Inler's shot deflected off Nigel de Jong's shin and into the top corner.
Higuain then had a goal ruled out for offside before Christian Maggio hit the post as AC Milan held on until half-time.
Argentina striker Higuain gave the hosts the lead as he glanced home Inler's left-wing cross and the points were sealed late on as he converted Jose Callejon's low cross.
It proved a frustrating night for Milan striker Mario Balotelli, who appeared to be in tears on the substitutes bench after being withdrawn.
Napoli will face Premier League Swansea in the last 32 of the Europa League on 20 February, while Milan entertain Atletico Madrid in the last 16 of the Champions League on 19 February.
- 88InlerBooked at 38minsSubstituted forDzemailiat 89'minutes
- 8JorginhoBooked at 68mins
- 17HamsikSubstituted forBehramiat 83'minutes
- 24InsigneSubstituted forCallejónat 78'minutesBooked at 87mins
- 4Adriano Buss
- 32AbbiatiBooked at 22mins
- 2De Sciglio
- 28EmanuelsonSubstituted forMontolivoat 70'minutes
- 34de Jong
- 45BalotelliSubstituted forPazziniat 73'minutes
- 7de SouzaSubstituted forDos Santos Leiteat 45'minutes
- 23TaarabtBooked at 54mins
- 22Dos Santos Leite
- 59Vasconcellos Ferreira
- Davide Massa
- Shots on Target
Second Half ends, Napoli 3, Milan 1.
Foul by Giampaolo Pazzini (Milan).
Federico Fernández (Napoli) wins a free kick in the defensive half.
Attempt saved. Blerim Dzemaili (Napoli) right footed shot from the centre of the box is saved in the bottom right corner.
Substitution, Napoli. Blerim Dzemaili replaces Gökhan Inler.
Raúl Albiol (Napoli) wins a free kick in the defensive half.
Foul by Giampaolo Pazzini (Milan).
José Callejón (Napoli) is shown the yellow card for a bad foul.
Foul by José Callejón (Napoli).
Mattia De Sciglio (Milan) wins a free kick on the left wing.
Foul by Gökhan Inler (Napoli).
Michael Essien (Milan) wins a free kick in the defensive half.
Faouzi Ghoulam (Napoli) wins a free kick in the defensive half.
Foul by Kaká (Milan).
Substitution, Napoli. Valon Behrami replaces Marek Hamsik.
Goal! Napoli 3, Milan 1. Gonzalo Higuaín (Napoli) right footed shot from the centre of the box to the bottom left corner. Assisted by José Callejón.
Attempt saved. Giampaolo Pazzini (Milan) right footed shot from the right side of the box is saved in the centre of the goal. Assisted by Riccardo Montolivo with a through ball.
Substitution, Napoli. José Callejón replaces Lorenzo Insigne.
Offside, Milan. Kaká tries a through ball, but Giampaolo Pazzini is caught offside.