Napoli missed the chance to return to the top of Serie A as they were held to a 1-1 draw by AC Milan at Stadio San Paolo on Monday.
Having beaten Napoli last weekend, leaders Juventus dropped points at Bologna on Friday, but Maurizio Sarri's men failed to make the champions pay as Sinisa Mihajlovic's in-form Milan demonstrated their recent improvement with a dogged display.
Napoli - who welcomed back Gonzalo Higuain and Lorenzo Insigne after being rested for the Europa League - enjoyed plenty of possession throughout and were on course for victory when Insigne opened the scoring 39 minutes in.
However, a rare lapse in concentration from Napoli's defence allowed Milan to level through Giacomo Bonaventura just before the interval.
Napoli again enjoyed plenty of the ball in the second half and Milan - unbeaten in Serie A since early January - survived a number of scares, including Dries Mertens hitting the post after the hour.
Mihajlovic's side were dispatched 4-0 in October's reverse fixture but demonstrated their improvement to claim an impressive point, while Sarri's frustrations got the better of him as he was sent to the stands by referee Luca Banti late on.
Having strengthened their line-up from the Europa League defeat to Villarreal, Napoli were on top in the early stages, although the pacy Carlos Bacca twice had sights on goal.
While Jorginho and Insigne fired over from distance, clear-cut chances proved few and far between until Cristian Zapata got a crucial block on Higuain's shot to send it wide 19 minutes in.
As Napoli piled on the pressure, Jose Callejon and Higuain went close before the hosts deservedly took the lead.
Insigne's low drive from outside the area deflected off Ignazio Abate before finding its way past Gianluigi Donnarumma and into the far corner of Milan's net.
However, the visitors levelled just five minutes later as Napoli switched off, allowing Bonaventura to convert Keisuke Honda's deep delivery at the far post on the stroke of half-time.
Sarri's men were on top after the restart but again struggled to convert possession into chances - Elseid Hysaj frustrating his team-mates by sending a shot high and wide as Napoli struggled for cohesion in the final third.
Donnarumma was required to deny Higuain what would likely have been a certain goal when he cut out Callejon's cross and, when the Spaniard was replaced by Mertens, the substitute went closest to a winner as he stroked Insigne's cross onto the post.
Sarri missed the final stages after being sent to the stands following a heated touchline discussion with the officials and, in his absence, Napoli threw everything at Milan, Higuain's shot deflected wide by Zapata, before substitute Omar El Kaddouri saw a late attempt saved by Donnarumma from close range.
Those final attacks were to no avail, however, as the Scudetto hopefuls were left to rue an opportunity missed against a tenacious and improving Milan side.