Turin (Italy): Uruguayan Jose Caceres and French recruit Paul Pogba scored a goal apiece as champions Juventus pulled three points clear of closest challengers Napoli with a 2-0 win on Saturday.
But AC Milan's problems continued when they slumped to a fifth defeat of the season, 3-2 at third-placed Lazio.
Juventus and Napoli went into the top-of-the-table clash, billed as a battle between the poor south and rich north, as the only two unbeaten teams in the league after seven games.
But after a dominant first half by Juve in which Sebastian Giovinco and Napoli striker Edinson Cavani came close to opening the scoring, Juventus quashed Napoli's hopes in two second-half minutes to claim their seventh win in eight games.
As Juventus coach Antonio Conte continues to sit out a suspension which ends in December, it was up to his assistant Angelo Alessio, taking charge on his first game back following his own suspension, to sing his team's praises.
"It was a good overall performance. I think the team showed their will to win, we were attacking while Napoli were relying on the counter attack," said Alessio.
"We've won seven of our eight games so far, we're well organised and we went out tonight to win. When we scored our opener, it was no surprise. We put six players up for that corner who could potentially score."
Napoli have been one of the most attack-minded teams in the league this season but on this occasion they were made to pay for their wait-and-see approach.
That did not stop coach Walter Mazzarri, however, from putting a positive spin on his players' display.
"I'm happy about our overall performance. I thanked the players one by one," said Mazzarri after Napoli's first defeat of the season left them three points behind the champions.
"It wasn't easy because we were up against one of the best teams in Europe. But we had more possession than Juve, we controlled the match more than Juventus and they scored against the run of play."
As early as the first minute Juve signalled their aims as Giovinco strolled into the area following a short corner to unleash a shot which Morgan De Sanctis did well to get low and collect.
Napoli's approach left Cavani, who returned to Italy only early Friday from Uruguay after international duty in midweek, with few scoring chances and he was most notable early on for picking up a largely unwarranted yellow card on 11 minutes after Juve defender Giorgio Chiellini ran into him.
Cavani, however, was unlucky not to score a stunning opener.
When Juan Zuniga found Gokhan Inler with a pass on the left of the area the slightest of tugs from Vidal brought the Swiss midfielder down.
From the resultant free kick Cavani shook the post and the crossbar as Juve keeper Marco Storari could only look on.
Juve, still pressing for the opener, came close on the stroke of half-time when the impressive Claudio Marchisio's shot from the edge of the area forced De Sanctis into action as it soared just over the crossbar.
Ghanaian midfielder Kwadwo Asamoah won a freekick just outside the area shortly after the restart and Andrea Pirlo's freekick took a deflection but was saved low by De Sanctis.
At the other end Napoli were given a rare glimmer of hope after a nice exchange of passes between Marek Hamsik and Goran Pandev, but as Pandev teed up his shot an alert Marchisio came chasing back to block.
Giovinco then wasted his second scoring chance when he fumbled Asamoah's pass in the area and regained control but sent his shot a metre past De Sanctis' upright.
Alessio replaced striker Fabio Quagliarella with Alessandro Matri, but two further substitutions shortly after were to prove most fruitful.
Pogba came on for Vidal while Asamoah went off to be replaced by Caceres and within minutes, Juve had taken a 2-0 lead.
With barely 10 minutes remaining Juve won a corner and Caceres got his head to Pirlo's cross to beat De Sanctis from close range.
Two minutes later a poor clearance from Napoli found Pogba over 20 metres out and the French teenager sent a superb strike past the diving De Sanctis to claim his maiden goal for the club.
Milan are down in 11th place while Lazio are third, on 18 points, four off the lead.
Lazio were 3-0 ahead by the 50th minute thanks to goals from Hernanes (25 min), Antonio Candreva (41) and Miroslav Klose (49).
Dutchman Nigel De Jong (61 min) and Stephan El Shaarawy (79) hit back for Milan but it was too little, too late.