The mistake was sufficient for the viola to take a point, with both Napoli and Fiorentina staying second and fifth respectively. As a result, Juve's gap at the top has now opened out to five points.
The opening half-chance fell for the visitors, though unfortunately for Napoli, it was for Goran Pandev. Marek Hamšík's ball from the left was volleyed by the Macedonian striker, though it unsurprisingly bounced harmlessly wide of Neto's goal.
Both sides were mostly inseparable for the opening quarter, with the formation match-ups ensuring that neither side had any time on the ball in midfield. Fiorentina's chief playmaker Alberto Aquilani was marked out of the game by Hamšík, while his teammates Valon Behrami and Gökhan Inler wrestled with Borja Valero and Romulo, and vice-versa.
It is telling, therefore, that the opening goal came as the result of a Morgan De Sanctis classic, rather than of any tactical advantage. Other than a penalty shout from Luca Toni and a close curling free-kick from Manuel Pasqual, Fiorentina had left the Napoli keeper mostly untroubled, though he soon rectified that himself, after mysteriously charging out of his goal towards a long ball from Facundo Roncaglia.
Getting caught up amongst Toni and his own defenders, the ball bounced over the stranded shot-stopper's head before landing in the back of the net. Cue a rather apologetic-looking Roncaglia -- who has now scored more goals this season than Goran Pandev -- and a rather apoplectic-looking Walter Mazzarri.
Napoli looked rattled after the goal, and only a crunching tackle from ex-viola defender Alessandro Gamberini prevented Juan Cuadrado squirming through on goal for an almost-certain second. Yet, despite the momentum firmly swinging the hosts' way, the scores were leveled with less than five minutes to go to the break.
Edinson Cavani headed the ball past Neto for his 100th Serie A goal after meeting a Hamšík free-kick from the left before all hell broke loose. Seconds later De Sanctis atoned for his own error by denying Luca Toni from six yards, before the veteran striker volleyed wide of goal.
The second half followed much the same narrative as the first; slow start before getting gradually more and more exciting. Cavani was the first to test Neto after the restart, though his effort from a tight angle just short of the hour was comfortably held at the near post.
Fiorentina saw more of the ball but were less efficient with it, seemingly content with the point, introducing gladiatorial midfielder Giulio Migliaccio. Napoli, however were desperate for all three, and pacey striker Lorenzo Insigne was introduced over defender Gamberini.
Gökhan Inler's effort from the edge of the area forced a diving save from Neto, before the Brazilian goalkeeper made a match-saving stop in keeping out a Pandev header from point-blank range. With the game wide open, Fiorentina had a couple of chances in stoppage time, though Jovetic volleyed a Cuadrado cross wide, and Aquilani skied his effort from the edge of the area.
Fiorentina (3-5-2): Neto; Stefan Savic, Gonzalo Rodríguez, Facundo Roncaglia; Manuel Pasqual (Nenad Tomovic 82), Alberto Aquilani, Borja Valero, Romulo (Giulio Migliaccio 77), Juan Cuadrado; Stevan Jovetic, Luca Toni (Adem Ljajic 85)
Napoli (3-4-2-1): Morgan De Sanctis; Miguel Britos, Alessandro Gamberini (Lorenzo Insigne 70), Hugo Campagnaro; Juan Zúñiga, Gökhan Inler, Valon Behrami (Blerim Džemaili 56), Christian Maggio; Marek Hamšík, Goran Pandev; Edinson Cavani
Goals: Roncaglia 33 (F) Cavani 42 (N)