Defender Gabbia rose highest to thump home Tijjani Reijnders' free-kick in the 89th minute and give Milan a Serie A win which pulls them out of a miserable early season slump.
Juventus were held to a 0-0 Serie A draw at Empoli on Saturday as Thiago Motta's side dropped more points after their goalless home stalemate against AS Roma before the international break.
Inter and AC Milan on Friday rejected the project to modernise and restructure the iconic San Siro stadium which they share, city mayor Giuseppe Sala announced.
Victor Osimhen has been sidelined by Napoli after the team he fired to Serie A glory just a over year ago left him both off their squad list for the 2024/25 campaign and potentially in season-long limbo.
Belgium striker Lukaku completed a permanent move to Napoli from Chelsea on Thursday, ending a long period of limbo with the Blues.
Inter Milan thrashed Atalanta 4-0 on Friday to move provisionally top of Serie A, while Torino snatched a late 1-0 win at Venezia to continue their positive start to the campaign.
The futures of Napoli striker Victor Osimhen and England international Ivan Toney are set to dominate the final day of the European transfer window on Friday as Chelsea continue their frenzied pursuit of new signings.
Napoli have signed Romelu Lukaku from Chelsea, the Serie A club announced on Thursday, ending the Belgium striker's extended period in limbo with the Blues.
Poland goalkeeper Wojciech Szczesny on Tuesday announced he was retiring from football at the age of 34 less than two weeks after the end of his contract with Juventus.
Napoli striker Victor Osimhen says if he leads the club to first Serie A title in more than 30 years, he will become a club "icon", but he would not be able to reach the status of late Argentine great Diego Maradona.
Matias Vecino's brilliant long-range strike earned Lazio a 1-0 win at Napoli on Friday as the runaway Serie A leaders lost for only the second time in the league this season.
Manchester United's reward for getting the better of LaLiga leaders Barcelona in the Europa League playoffs is a last-16 clash with another Spanish side Real Betis, while Premier League table-toppers Arsenal will face Portuguese outfit Sporting.
Simone Inzaghi's side stay second and are three points ahead of local rivals AC Milan, who beat Monza 1-0 earlier on Saturday, but are a long way behind rampant Napoli after their 2-0 win at Sassuolo on Friday.
It looks only a matter of time before Luciano Spalletti's rampant side secure a Scudetto dreamed of by Napoli fans since the days of Diego Maradona
A 33-year wait for the league crown looks closer to ending for Napoli
Milan last won a game over a month ago
Italian media report that Galatasaray offered Roma 16.5 million euros ($17.7 million) with add-ons of up to 13 million euros to take Zaniolo off their hands.
AC Milan's crisis threatens to deepen as the champions head into Sunday's derby with Inter, miles off the Serie A title pace and in a battle to reach next year's Champions League.
Juventus will face Inter Milan in the last four of the Italian Cup after beating Lazio 1-0 in Thursday's final quarter-final tie.