An Edin Dzeko header was enough for Inter to beat Napoli 1-0 at San Siro on Wednesday and end the Serie A leaders' unbeaten start to the season.
After their closest challengers Milan beat Salernitana away earlier the same day, Napoli's lead at the top was cut to five points as the Partenopei began 2023 in underwhelming fashion.
Inter were unfortunate not to be ahead at the break after Federico Dimarco and Romelu Lukaku missed great first-half opportunities.
But Dzeko powerfully nodded home the winner 10 minutes after half-time, as Inter remain in fourth but crucially move within eight points of Napoli at the summit in their bid to chase Luciano Spalletti's side down.
Inter should have been ahead within four minutes, but Dimarco could only fire over after Lukaku picked him out at the back post.
Dimarco's fellow wing-back could not do any better, Matteo Darmian failing to hit the target after excellent link-up play between Lukaku and Dzeko set him up.
Lukaku missed a golden opportunity before the break, latching onto a throughball but wildly firing over as Inter failed to take advantage of their superior chances in the opening 45 minutes.
But they eventually capitalised in the 56th minute when Dimarco's pinpoint delivery from the left found Dzeko in space to power a header past Alex Meret.
Khvicha Kvaratskhelia nearly got a rapid equaliser as he slammed into the side-netting.
The visitors pushed for an equaliser late on, but Inter held out despite Giacomo Raspadori stinging the palms of Andre Onana with a fierce effort in the dying seconds.
What does it mean? Napoli stumble as Inter make up ground
Prior to the World Cup break, it appeared nobody would get a sniff of beating Napoli to the Serie A title as they reeled off 11 straight league victories.
They looked a shell of that team here however, casting real doubt over their ability to sustain their previously rampant title charge.
Inter were the better team, registering 1.24 xG (expected goals) to Napoli's 0.96 and creating three Opta-defined 'big chances' to their opponent's one. Spalletti's side will need a quick improvement if they are to get their campaign back on track.
Dzeko the hero
Inter may have been wondering whether this would be a wasted opportunity to reduce the deficit to the summit after missing a string of first-half chances, but 36-year-old Dzeko popped up with the winner to earn all three points.
The former Manchester City striker led Inter with five touches in the opposition box and was ruthless, finishing his only big chance with a thundering header.
Off day for Osimhen
Napoli forward Victor Osimhen is Serie A's top scorer with nine goals already this campaign, but he was kept very quiet by Inter's centre-backs.
Milan Skriniar, Alessandro Bastoni and Francesco Acerbi restricted the Nigeria international to just 19 touches – the fewest of all 22 starters and half of Napoli goalkeeper Meret's 38 – and two shots, highlighting his general lack of influence.
Key Opta facts
- Napoli have lost for the first time in Serie A this season after 13 wins and two draws; this was their first league defeat since April 2022 (2-3 against Empoli).
- Edin Dzeko has scored 20 Serie A goals for Inter, each of them after turning 35: all the other Inter players who have found the net at 35+ years old in the competition have scored 19 in total.
- Inter have won their first Serie A match of the calendar year for the fourth consecutive year; indeed, they are unbeaten in each of the last nine (W6 D3).
- Inter have won each of their last two meetings against the team at the top of the table at the start of the matchday in Serie A; the last such occasion was also against Napoli at San Siro, in November 2021.
- Edin Dzeko has been involved in five goals in his last three league appearances, as many as in the previous 22.
Both teams are in Serie A action again at the weekend, with Inter travelling to Monza on Saturday while Napoli are away at Sampdoria the following day.