Napoli kept their early lead of Serie A after Sunday's goalless draw at Fiorentina, while Atalanta's 1-0 win at Verona ensured they moved level with the early pacesetters.
Luciano Spalletti's Napoli were less flamboyant than in their opening two victories but had marginally the better of the opportunities in an absorbing encounter at the Stadio Artemio Franchi.
Not even the introduction in the second half of lively new signings Giacomo Raspadori, Giovanni Simeone and Tanguy Ndombele could push the away side to the win.
After the match Spalletti was angry with a group of Fiorentina fans near the away dugout who he confronted after being insulted for nearly the entire match.
"They dished out insults from behind the bench from the start to the end, right near where children were sitting," he told DAZN.
"They were saying 'your mum, your mum', she's 90 years old, the poor thing."
The stalemate puts Napoli on seven points from their opening three matches, level with six teams including champions AC Milan and Atalanta, ahead of their match with Lecce on Wednesday as a punishing fixture pile-up looms.
Fiorentina, who are also unbeaten, sit ninth on five points.
An intense contest in Florence began with the hosts on the front foot and they went closest to taking the lead midway through the first half when after Alex Meret spilled Riccardo Sottil's shot, Giacomo Bonaventura flashed a low drive just wide.
Victor Osimhen had a tap-in ruled out for offside just before the break as Napoli grew into the game, and the away side should have been ahead not long after the restart.
Amir Rrahmani headed Piotr Zielinski's cross narrowly over in the 48th minute. Then, just after the hour mark, Hirving Lozano wasted a golden chance to put Napoli ahead.
Khvicha Kvaratskhelia, in less eye-catching form than in hs first two games, dangled the most inviting of crosses from the right which Mexico attacker Lozano somehow headed wide from close range.
Raspadori came on after an hour and was denied the winner with eight minutes of his debut remaining, Pierluigi Gollini getting down well to push the Italy international's low shot wide.
Earlier Teun Koopmeiners drilled home a powerful winner four minutes after half-time at the Stadio Bentegodi to keep Atalanta unbeaten.
Gian Piero Gasperini's side missed good chances to make the win more comfortable and would have taken only a point back to Bergamo had Darko Lazovic's 63rd-minute strike from distance bounced in rather than out off the bar.
"We're still completing the squad as we kind of stuck between injuries and new arrivals," said Gasperini to DAZN.
"We're looking for the right format which will make us most effective."
Salernitana sit a point behind Fiorentina in 10th after they hammered Sampdoria 4-0 thanks in large part to Boulaye Dia, who opened the scoring in the seventh minute and set up two more on his full debut for the club.
Dia, on loan from Villarreal, tapped home Federico Bonazzoli's low cross and, although his goal was initially ruled out for offside, a VAR check overturned the decision and put the hosts ahead.
Dia then turned provider for Bonazzoli's superb strike which double Salernitana's lead with a quarter of an hour gone.
Tonny Vilhena made sure of the three points in the 50th minute when he delicately finished off Lassana Coulibaly's chipped through ball after a beautiful passing move.
Erik Botheim completed the rout with 14 minutes remaining with a perfect low finish from Dia's pass which slid past Emil Audero and in off the post.
A humbling defeat and Lecce's 1-1 draw with Empoli dropped Samp, who are yet to score this season, into the drop zone with a single point.
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