Napoli missed the chance to move back to the top of Serie A after it was held by AC Milan to an entertaining 1-1 draw on Monday.
Napoli lost the top spot to Juventus a week ago but could have reclaimed first place with a win following Juve's draw at Bologna on Friday.
It remained a point behind the four-time defending champion.
Milan, which has only lost one match this year, picked up a precious point in its fight for third place and the final Champions League spot. It was eight points behind Fiorentina.
Lorenzo Insigne fired Napoli in front six minutes from halftime when his effort was deflected into the bottom right corner.
However, Milan leveled five minutes later as Napoli defender Kalidou Koulibaly could only head Keisuke Honda's cross to Giacomo Bonaventura, who volleyed into the near corner.
Dries Mertens came agonizingly close to restoring Napoli's lead in the second half but hit the left post with Milan goalkeeper Gianluigi Donnarumma beaten.
Milan's teenage shot-stopper pulled off a couple of crucial saves in the dying minutes, while Napoli striker Gonzalo Higuain side-footed inches wide of the left post from close range.
Milan also went close to snatching a winner but M'Baye Niang fired wide from a great position, and Honda's low strike was palmed around the post by Pepe Reina.
Napoli coach Maurizio Sarri was sent to the stands in the 73rd for dissent.