Gonzalo Higuain overcame a fractured hand to help Juventus pull within a point of leaders Napoli in the Serie A title race, scoring the decisive goal in a tight 1-0 win over his former club.
Higuain had been a doubt for Friday's contest against the team he left for Juve in a €90million move in July last year after undergoing surgery on his left hand.
But the Argentina striker was named in the starting XI and needed just 12 minutes to make what proved to be the key contribution as Juve boosted their momentum in the hunt for a seventh successive Scudetto, while Napoli's hopes of a first league title since the 1989-90 season hit an early setback.
Napoli have lit up both Serie A and the Champions League this season with their entertaining and free-scoring style of play under Maurizio Sarri.
Yet they were frustrated following Higuain's opener, with Gianluigi Buffon untested in the Juve goal in the second half. The Turin club are now second - a point ahead of Inter, who can go top with a win over Chievo on Sunday, having played a game more - and remain three clear of Roma, who beat SPAL 3-1 in the day's earlier game.
Both teams must quickly turn their attention to Champions League football in midweek, with Napoli taking on Feyenoord and Juventus visiting Olympiacos as they each bid to seal a place in the last 16.
Higuain forced Pepe Reina into action in the fourth minute as he was denied at the near post after being played in by Douglas Costa.
The same two players were involved when Reina was beaten eight minutes later.
Costa started a quick counter-attack and Paulo Dybala's superb pass found Higuain, who slotted the ball inside Reina's left-hand post.
Napoli responded well, though, and Marek Hamsik forced Buffon to parry behind with a long-range strike.
But Costa continued to cause Napoli problems on the break, another marauding run leading to a cutback that Higuain saw deflected for a corner, from which Medhi Benatia lashed wide.
Lorenzo Insigne curled towards the roof of the net only to be thwarted by Buffon, who then kept out his header from the resulting corner.
Dybala threatened to double Juve's lead before the break, but could not produce the finish to match his surge into the Napoli half.
Jose Callejon flashed a shot wide as Napoli continued to be frustrated despite dictating the play, and the San Paolo grew further exasperated when the hosts were denied a penalty when Dries Mertens went down as he battled for the ball with Giorgio Chiellini.
Napoli were grateful to Reina for keeping them within touching distance in the 68th minute, the Spaniard turning over Blaise Matuidi's strike into the ground after the France midfielder latched on to Miralem Pjanic's perfectly weighted cross-field ball.
Insigne drove wide of the far post on the half-volley in what was Napoli's last legitimate chance, Juve successfully sitting deep to secure a result that will, despite Napoli's position at the summit, reaffirm their status as title favourites.