Napoli dropped points for the second successive Serie A match as they were held to a 0-0 draw at Inter, failing to reclaim top spot and handing Juventus the advantage in the title race.
Juve put the pressure on Napoli by beating Udinese 2-0 earlier on Sunday and Maurizio Sarri's men were unable to break Inter down to return to the summit, having suffered a 4-2 home defeat to Roma last time out.
Napoli dominated the majority of the first half and played some fine football at times, but they had no luck when trying to cut through Inter's stubborn defence, the hosts managing to prevent Sarri's side from creating any clear-cut chances before the break.
The contest opened up a little more upon the restart and Milan Skriniar nearly put Inter ahead, hitting the post with a header.
Although opportunities remained rare for Napoli, Lorenzo Insigne wasted a glorious one just after the hour mark as the visitors tried to mount a late onslaught.
Inter held firm, however, meaning Napoli finish the weekend a point behind Juve, who play their game in hand against Atalanta on Wednesday.
True to their style, Napoli quickly looked to become the dominant force and dictate the tempo of the contest.
But that did not result in a flurry of chances, as Inter sat deep, absorbed pressure and successfully kept their visitors at arm's length.
Napoli resorted to shooting from distance, though accuracy was lacking, as Insigne shot wide from 30 yards, before Marek Hamsik sliced well over from a similar distance in the 25th minute.
The best chance of the first period actually fell to Inter seven minutes from the break, as they took the rare opportunity to venture into Napoli's half and Antonio Candreva shot just wide of the bottom-left corner from 20 yards after cutting in from the right flank.
Proceedings became less cagey after the break and Napoli almost found themselves trailing, but luckily for them the post came to their rescue, denying Skriniar's header from Joao Cancelo's cross.
Insigne shot just wide from long range for a second time soon after, but still Inter looked the more likely to break the deadlock – Kalidou Koulibaly nearly putting into his own goal when meeting Candreva's cross.
The chance Napoli had seemingly been waiting for eventually arrived 23 minutes from time, but Insigne spurned it, opting to try to chip Samir Handanovic after being played through by Dries Mertens, seeing his effort land on the roof of the net.
Another opportunity fell to the wasteful Insigne 10 minutes from the end and again he failed to take it, shooting over from the edge of the box in what proved to be the final chance, with Napoli left to reflect on a potentially damaging result.
