Milan - Luis Muriel hit a hat-trick as Atalanta put their midweek Champions League humiliation behind them with a crushing 7-1 win over 10-man Udinese on Sunday that moved them to within three points of Serie A leaders Juventus.
Gian Piero Gasperini's side consolidated third place with 20 points from nine games, two adrift of second-placed Inter Milan and three ahead of Napoli, who were held 1-1 at lowly SPAL.
Defending champions Juve stay top despite drawing 1-1 at Lecce on Saturday thanks to Antonio Conte's Inter also collecting just a point with their 2-2 draw with Parma.
Roma moved up to fifth, one point behind Napoli, with Edin Dzeko scoring and setting up Nicolo Zaniolo for the winner in a 2-1 victory that plunged AC Milan further into crisis.
City rivals Lazio are just behind Roma in sixth after Serie A top scorer Ciro Immobile snatched a 2-1 win at Fiorentina.
Gasperini said his side, top scorers with a Serie A-record 28 goals after nine games, had felt bitterness after their 5-1 humbling at Manchester City, their third Champions League defeat in as many games.
"We're trying to use the Champions League to gain experience and it helps us become better in Serie A, to fight back from difficult situations, like when we went behind today," said Gasperini.
"We're not deluding ourselves. It is very early days, only nine rounds," he continued.
"The Scudetto is Juventus's to lose, then there are Inter and Napoli as well as other teams that have important possibilities."
After falling behind after 12 minutes following Stefano Okaka's first away goal for Udinese this season, the Bergamo side got into their stride.
Slovenian Josip Ilicic picked up a Marten De Roon cross to grab the equaliser after 21 minutes, and it was all one-way traffic after Udinese's Nicholas Opoku was sent off after picking up a second yellow card for bringing down Ilicic.
Muriel converted from the spot for the first of his treble, which included two penalties, with Slovenian Ilicic completing a first half brace.
Mario Pasalic also got on the scoresheet and 17-year-old Ivorian forward Amad Diallo Traore completed the rout to score on his debut seven minutes from the whistle.
Udinese, meanwhile, are 13th but just three points away from the drop zone.
Atalanta next travel to Napoli's San Paolo Stadium on Wednesday after Carlo Ancelotti's side were held to their second stalemate in three Serie A games.
After winning 3-2 a European thriller in Salzburg, Arkadiusz Milik put Napoli ahead after nine minutes.
But their advantage was cancelled out seven minutes later by SPAL's Jasmin Kurtic.
Napoli also had a penalty awarded before the break for a Francesco Vicari handball only to see it overturned after a VAR viewing.
"We couldn't have done more today," said Ancelotti.
"Even Juve and Inter, with yesterday's draws, lost an opportunity. Everyone in the week is paying for something in the Champions League."
Injury-hit Roma ended their run of four consecutive stalemates to move fifth as new Milan coach Stefano Pioli took his first defeat since taking over two weeks ago.
Dzeko, wearing a face mask to protect his fractured cheekbone, headed in the opener seven minutes before the break.
Milan defender Theo Hernandez pulled the visitors level on 55 minutes with a goal that took a slight deflection, but four minutes later Dzeko connected with Zaniolo for the winner, to send Milan down to 12th, three points above the relegation places.
In Tuscany, Lazio captain Immobile headed in his 10th goal this season after 89 minutes to condemn Fiorentina to their first league defeat in nearly two months.
Joaquin Correa opened the scoring for the visitors after 22 minutes but Federico Chiesa levelled five minutes later following good work by Franck Ribery.
Jordan Lukaku found Immobile with the clock ticking and he nodded in, with Felipe Caicedo missing a chance for a third, with goalkeeper Bartlomiej Dragowski denying his penalty chance.
Surprise package Cagliari are seventh after a 1-1 draw against midtable Torino, who stretched their winless run to four games.
Claudio Ranieri fell to his first defeat as coach of rock bottom Sampdoria, losing 2-1 to Bologna.