Napoli's hopes of closing the gap on Juventus at the top of Serie A to two points were dashed on Sunday following a subdued performance in a 0-0 home draw with Sampdoria.
Fiorentina, shaping up as rivals to Napoli in the chase for a Champions League spot, got back to winning ways with a 4-1 thrashing of dismal Inter Milan.
With leaders Juve losing 1-0 at AS Roma on Saturday, second-placed Napoli were looking to put the pressure on their Turin rivals and bounce back after a 3-0 home Europa League defeat by Viktoria Plzen.
After a minute's silence to remember former Napoli player Carmelo Imbriani, who died of cancer on Friday at the age of 37, it was the visitors who came out in determined mood with Gianluca Sansone going close.
Napoli responded well, though, with Lorenzo Insigne letting fly from distance and Edinson Cavani fluffing a shot into the arms of goalkeeper Sergio Romero. Goran Pandev came off the bench to link up nicely with Marek Hamsik whose powerful shot was only kept out by a full-stretch Romero.
Juventus, however, remain in touching distance just four points above with the two sides due to meet next month.
Napoli coach Walter Mazzarri did not speak to the press but sporting director Riccardo Bigon said this was because of illness. "We remain convinced that we have our future in our hands," he said. "We created plenty of chances against Sampdoria, we're still optimistic about our chances in this title race.
"Mazzarri? He's not well. He's got a 38-degree temperature, he's gone home to get some rest."
Sampdoria assistant coach Fedele Limoni was delighted by his side's performance.
"We worked really hard defensively, we gave very little away to Napoli," he said. "The pitch? It's the same for everybody. It was a problem for us when it came to trying to find space, it certainly did affect us."
Goals from Adem Ljajic and Stevan Jovetic ensured a comprehensive win for Fiorentina over Inter in front of an ecstatic home crowd. Fiorentina dominated the first half and it was only a fine display from keeper Samir Handanovic that kept the scoreline respectable.
Fiorentina took the lead in the 13th minute after Jovetic flicked a cross by Manuel Pasqual to Ljajic who got in front of defender Juan Jesus to beat Handanovic with a diving header from close range.
Jovetic then shrugged off the attentions of Andrea Ranocchia before curling in a fine shot from the left-hand side of the penalty area with the keeper rooted to the spot.