An extraordinary Zlatan Ibrahimovic header has given Milan the half-time lead, but Napoli forced saves and clipped the crossbar.
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This was a head-to-head for the top of the table, with Sassuolo having leapfrogged both with a 2-0 win at Verona earlier this afternoon.
Stefano Pioli and another five members of his staff were self-isolating with COVID, so Daniele Bonera was the makeshift coach. Rafael Leao was injured, but Ante Rebic had his first start in two months after dislocating his elbow. The Partenopei missed Victor Osimhen, Elseid Hysaj and Amir Rrahmani, but kept the 4-2-3-1 formation with Dries Mertens in a more advanced role.
Matteo Politano forced Simon Kjaer into a desperate interception, but Milan had the stronger start, as Alex Meret palmed a Hakan Calhanoglu rocket round the post and on the resulting corner, Kjaer shinned over from six yards.
Ibrahimovic broke the deadlock with a magnificent goal, as he got in front of Kalidou Koulibaly to steer his header into the far bottom corner from 12 yards on a Theo Hernandez cross. It means Ibrahimovic is only the fourth player in the three points for a win era to score in his first six games of the season.
Napoli fought back in waves, as Gianluigi Donnarumma got down to palm a Mertens effort round the post. On the resulting corner, there were three huge chances in one move, as Tiemoue Bakayoko’s shot was parried by Donnarumma, Giovanni Di Lorenzo fired onto the bar and Hirving Lozano’s follow-up was fingertipped over.
Mertens also tested Donnarumma from a tight angle after Insigne floated a free kick over the top.
Napoli 0-1 Milan (Half-Time)
Ibrahimovic 20 (M)
Napoli: Meret; Di Lorenzo, Manolas, Koulibaly, Mario Rui; Fabian Ruiz, Bakayoko; Politano, Lozano, L Insigne; Mertens
Milan: G Donnarumma; Calabria, Kjaer, Romagnoli, Theo Hernandez; Kessie, Bennacer; Saelemaekers, Calhanoglu, Rebic; Ibrahimovic
Ref: Valeri