A cagey start to the game saw both sides struggle to create notable goal-scoring chances, although the hosts were the slightly better side. They went ahead at the hour mark after Juventus captain Giorgio Chiellini was adjudged to have struck Amir Rrahmani with his elbow.
Insigne stepped up to take the ensuing penalty, making no mistake from 12 yards out, as he rifled his shot into the roof of the net. That was only the second goal conceded by the visitors in their last seven games in all competitions.
The second half saw Juventus up the ante in a bid to grab the equaliser, but a resolute Napoli defence held firm. The visitors were limited to creating chances from set-pieces, but Cristiano Ronaldo squandered most of the opportunities.
Both managers made changes in the second half, with Gennaro Gattuso trying to protect his lead, while Pirlo sought extra bite in attack. The visitors had the ball in the back of the net in the 63rd minute, but Alvaro Morata was pulled up for offside.
A late chance fell the way of the Spanish striker, but Alex Meret produced a stunning save to deny the Juventus striker from point-blank range. The win saw Napoli close the gap on the Bianconeri and move into the top four.
On that note, let us have a look at five talking points from the game.
#5 Napoli bounce back from a testing week with a win
Napoli came into this game on the back of a three-game winless run that had seen them eliminated from the Coppa Italia and drop down the 2020-21 Serie A table.
Their performances in consecutive defeats to Genoa and Atalanta saw many question the team's mentality and Gattuso's managerial prowess.
However, such insinuations were laid to rest with a comprehensive performance against Juventus. Napoli dictated proceedings from start to finish, with Meret barely threatened until the dying stages of the game.
The win sees Napoli close the gap on Juventus to two points. Although they are still some way off the league summit, the San Paolo outfit have responded to critics in the best way possible.
#4 Juventus suffer a huge blow to their title hopes
Juventus, the nine-time Serie A defending champions, had high hopes of making it ten in a row coming into the season.
But they have started the campaign slowly and are playing catch up. Recent results have been positive, and that helped them close the gap on the league leaders.
However, a run of six consecutive wins in all competitions was halted by a goalless draw with Inter Milan in midweek. But Juventus would have fancied all three points against Napoli.
The Bianconeri, though, failed to get the job done despite seeing most of the ball. The defeat means Juventus could lose further ground in the Serie A title race.
The defending champions could fall ten points behind table-toppers AC Milan at the end of the gameweek. Although Juventus have a game in hand, a successful title defence is already looking like a very tall proposition for the embattled Bianconeri.