MILAN - Napoli came from behind to beat Sassuolo 3-1 and move provisionally four points clear at the top of Serie A after Inter Milan was held at Atalanta to 1-1 on Saturday.
Gonzalo Higuain scored twice to take his tally to 20 league goals, while Jose Callejon netted his first to cancel out Diego Falcinelli's third-minute opener from the spot for Sassuolo.
Juventus can cut the gap back to two points if it beats Udinese on Sunday for a 10th consecutive win. Also, Fiorentina could move above second-place Inter with a win at AC Milan.
Inter's title challenge suffered another blow, after it fell off top spot last week following a surprise defeat to Sassuolo. Atalanta, loser of its last four matches, was the stronger side and Inter goalkeeper Samir Handanovic had to pull off some fine saves, including a stunning stop on the hour mark.
Both sides netted own goals in the first half with Inter defender Jeison Murillo giving Atalanta the lead before Rafael Toloi also turned into his own net.
"I'm not happy with the performance of some of the players," Inter coach Roberto Mancini said. "We have good players, and we have to do more, especially up front. ... We won so many 1-0, and I would sign to win as many more, but sometimes one goal is not enough.
"At the beginning, we would have signed to find ourselves in this position at this point of the season, but that doesn't mean we have to waste everything we have done: We have to remain calm and get back to not giving away goals."
Atalanta slipped to 12th after Torino beat relegation-threatened Frosinone 4-2, ending a run of three consecutive defeats.
Napoli had lost only once in all competitions since an opening day defeat at Sassuolo, but Eusebio Di Francesco's side was the only team unbeaten against the top six.
It looked like that record was set to continue when it was awarded an early penalty after Nicola Sansone was brought down by Raul Albiol. Falcinelli converted to get visiting Sassuolo off to a good start.
It was end-to-end action, and Napoli levelled as Callejon headed in a pinpoint cross from Lorenzo Insigne.
Higuain fired Napoli in front from almost the same position three minutes from halftime, timing his run perfectly to get between two defenders and slot Marek Hamsik's cross into the far right corner.
Both sides had chances in the second half before Higuain sealed the result with the last kick of the game, managing to squeeze the ball between a diving Andrea Consigli and the post, following an assist by Callejon.
In Bergamo, Atalanta started the stronger and took the lead when Murillo slid in to intercept Boukary Drame's cross from the left, but succeeded only in poking the ball past his own goalkeeper.
Atalanta returned the favour eight minutes later as, following a delightful one-two between Mauro Icardi and Stevan Jovetic, Toloi fired into his own net off the underside of the crossbar.
Handanovic kept Inter in the match, and pulled off what could be the save of the season. Wearing a baseball cap to keep the sun out of his eyes, he somehow managed to stop Luca Cigarini's effort from point-blank range with his trailing foot.
"Handanovic's save? Impossible, I don't understand how he could have done it," Atalanta coach Edy Reja said. "Maybe we deserved more, even if Inter could have also punished us at the end. We have to continue like this."
Ciro Immobile marked his Torino comeback by converting an early penalty. Immobile, who spent 18 months at Bayer Leverkusen and Sevilla, had to retake the penalty because of encroachment but netted both kicks.