Inter handed Serie A leaders Napoli their first defeat of the campaign as Hakan Calhanoglu recorded a goal and an assist in a 3-2 home victory on Sunday.
Napoli had not scored in any of their past four away league games against the Nerazzurri but Piotr Zielinski netted their first since April 2017 after 17 minutes to open the scoring at San Siro.
Calhanoglu soon leveled from the penalty spot before assisting Ivan Perisic's header that put Inter into the lead before the interval.
Lautaro Martinez added a third just after the hour mark and, despite a wonderful strike from substitute Dries Mertens, the reigning champions triumphed to close the gap on Milan and Napoli to four points at the summit, ending the visitors' 21-match unbeaten Serie A run in the process.
Martinez headed over as the highest scorers in the division looked to strike first against a defense that had conceded just four goals this term.
However, it was Napoli who took the lead when Zielinski arrowed into the top-right corner from the edge of the area following Lorenzo Insigne's offload.
That advantage lasted all of eight minutes as Calhanoglu rolled his spot-kick into the bottom-left corner after VAR deemed Kalidou Koulibaly to have handled Nicolo Barella's effort.
Calhanoglu turned provider for Inter's second as Perisic flicked the Turkey international's corner past David Ospina a minute before half-time.
Napoli's task mounted further when Martinez drilled into the bottom-left corner after Joaquin Correa's pass on the counter.
Inter seemed set for a comfortable victory until Mertens fired into the top-left corner after Koulibaly dispossessed Edin Dzeko, though the hosts managed to cling on thanks to Samir Handanovic tipping Mario Rui's late header onto the crossbar.