A superb equaliser from Arturo Vidal earned Juventus a 1-1 draw at Inter Milan in the day's early game, an intriguing Derby of Italy which suggested Walter Mazzari's Inter side could challenge for the title this season.
Napoli's maintained their 100 percent record to move to nine points, while Inter and Juve are two points behind and Milan are in sixth place with four.
Argentine Higuain's second goal of the season came on 70 minutes in Napoli's tense match with Atalanta, in which Rafael Benitez's side struggled to break down the away side and had a flying Pepe Reina save to thank for not going behind to German Denis' long-range effort two minutes after the break.
The hosts started quickly, but after Goran Pandev failed to convert an easy looking chance in the 13th minute they laboured and it took until the introduction of Jose Callejon and Marek Hamsik midway through the second half for Napoli to take charge.
Hamsik's aggressive pressing led to the opening goal, with the ball falling to former Real Madrid striker Higuain who rolled home a calm finish.
Callejon sealed the three points 11 minutes later with his third goal in as many games, a similarly composed strike following a neat assist from Lorenzo Insigne.
Milan looked down and out 71 minutes into their clash with Torino, after two superb goals from Danilo D'Ambrosio and Alessio Cerci.
A bizarre Sulley Muntari goal three minutes from time, in which the midfielder scuffed a shot past out-of-position Torino keeper Daniele Padelli, gave Milan hope.
As Milan players celebrated no-one appeared sure if the goal had even been awarded, with Balotelli both looking offside and having fouled Padelli in the build up to the goal.
Balotelli then earned Milan a point deep into stoppage time when he scored from the spot after Andrea Poli was crudely upended in the area.
Walter Mazzari's Inter took the lead against reigning champions Juventus on 73 minutes through Mauro Icardi's first goal for the club following fine work from Ricky Alvarez.
But Juve equalised two minutes later when Vidal expertly controlled Kwadwo Asamoah's drilled cross before clipping past Inter keeper Samir Handanovic for his third goal in as many games.