Napoli forward Lorenzo Insigne celebrates after scoring during against Fiorentina.

CARLO HERMANN AFP

MILAN -- Lorenzo Insigne's stellar start to the season continued Sunday as he helped Napoli beat Serie A leader Fiorentina 2-1.

Insigne -- who had to pull out of the Italy squad last week through injury -- opened the scoring in the first minute of the second half with his sixth goal of the season, setting a new personal record.

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Nikola Kalinic leveled for Fiorentina in the 73rd minute but Gonzalo Higuain fired Napoli back in front just two minutes later.

Inter Milan can now move ahead of Fiorentina, which has 18 points, if it beats Juventus in the Derby d'Italia later.

Napoli moved into fourth place, three points behind Fiorentina, and above Lazio on goal difference after the capital side lost 2-1 at Sassuolo -- which also now has 15 points.

Atalanta was a point further back after easing past Carpi 3-0.

Elsewhere, substitute Panagiotis Tachtstidis -- who had only just come off the bench -- scored a stoppage-time winner as 10-man Genoa snatched a 3-2 win over Chievo Verona.

Newly-promoted Frosinone beat Sampdoria 2-0 and Hellas Verona drew 1-1 against Udinese, while Palermo won 1-0 at bottom side Bologna in the lunchtime kickoff.

Fiorentina was two points clear at the top of the table coming into the match, having won six of its seven games. But Napoli was also full of confidence after a 4-0 victory at AC Milan last time out.

Fiorentina started brightly and went close to taking the lead in the 17th minute but Pepe Reina did well to deny Jakub Blaszczykowski with a one-handed diving save.

Napoli could have gone in front on the stroke of halftime as Higuain's header from Insigne's cross flew just wide of the right-hand post.

It did take the lead just 43 seconds after the break, when Insigne burst past Nenad Tomovic down the left and ran onto Marek Hamsik's deep ball before cutting in to fire a low shot into the bottom right corner.

Kalinic leveled with a similar goal, outsprinting the Napoli defenders and running onto a brilliant Josip Ilicic ball over the top, to score his fifth goal in eight Serie A matches.

But Napoli was immediately back in front when Higuain beat Ilicic to the ball, played a swift one-two with Dries Mertens and fired past Fiorentina goalkeeper Ciprian Tatarusanu.

Domenico Berardi returned from injury for Sassuolo and had an immediate impact as he gave his side a seventh-minute lead from the penalty spot after Senad Lulic was harshly adjudged to have brought down Paolo Cannavaro.

Lazio almost leveled immediately but Sergej Milinkovic-Savic headed Antonio Candreva's cross off the crossbar.

Sassuolo doubled its advantage on the hour. Nicola Sansone scuffed a Sime Vrsaljko cross, but Simone Missiroli ran in behind to finish it off.

The home side almost sealed the result moments later but Diego Falcinelli's effort crashed off the crossbar.

It was almost made to rue that missed opportunity as Lazio reduced the deficit in the 67th when Keita Balde Diao slotted the ball across to Felipe Anderson who placed it into the bottom left corner.

Any hope Lazio had of snatching something from the match evaporated when Danilo Cataldi was sent off for a second booking in stoppage time.