Serie A leaders Napoli surrendered their unbeaten start to the season as Juventus striker Gonzalo Higuain returned to haunt his former club with the only goal in a 1-0 win.
Higuain was a major injury doubt before the game after undergoing surgery on a broken bone in his left hand earlier this week, but was named in the starting XI by head coach Massimiliano Allegri.
And the gamble paid off as Higuain's 12th-minute strike proved the difference between the two sides at the Stadio San Paolo, lifting Juventus to second in the table and just a point behind their fierce rivals.
The visitors started brightly and Higuain - who left Naples for Turin for 90 million euros in July 2016 -- almost broke the deadlock with just four minutes on the clock after being played in by Douglas Costa, but his shot was well saved by Pepe Reina.
But there was not much Reina could do to prevent the Argentina international opening the scoring after 12 minutes as Juve launched a swift counter-attack which saw Paulo Dybala set up Higuain to fire home from 10 yards.
Higuain was clattered by Kalidou Koulibaly's despairing challenge in the process of scoring, but was instantly back on his feet to celebrate a fifth goal in as many games against Napoli.
That unsurprisingly provoked a response from the home side and Lorenzo Insigne curled a shot over the crossbar before Marek Hamsik's effort was punched clear by Gianluigi Buffon.
Insigne again tried his luck from long distance after 37 minutes but a weak effort was easily gathered by Buffon, who repeated the trick against the same player just before the interval.
Buffon was equal to far tougher tests in the second half and did well to prevent Jose Callejon turning home a cross at his near post before Napoli appealed for a penalty as Dries Mertens burst into the box before going down under pressure from Giorgio Chiellini.
The referee was unconvinced, however, and Juventus almost doubled their lead moments later when Blaise Matuidi's volley from six yards out looked destined for the back of the net until Reina somehow turned the ball over the bar.
Napoli threw everything into an increasingly-desperate search for the equaliser with Reina coming forward for a corner three minutes into second-half stoppage time, but it came to nothing and Juventus held on for a potentially significant win in the title race.