The Uruguayan netted either side of half-time and Lavezzi grabbed a late third to secure a precious victory and move Walter Mazzarri's men ahead of Roma and Inter in the table
Edinson Cavani bagged a brace, netting one in each half, before Ezequiel Lavezzi wrapped up the win in injury time to ensure their side would follow up Monday's 2-0 win against Chievo with another precious three points.
The result sees the Partenopei climb two places and move ahead of both Roma and Inter, who lost 3-0 to Bologna on Friday.
Napoli made a lightning start, taking the lead in the third minute after their Three Tenors combined to carve their way through the Fiorentina defence.
Lavezzi started the move, cutting in off the right and threading the ball to Marek Hamsik, who then slipped Cavani in on goal with a visionary reverse pass. And the Uruguayan made no mistake, slotting under keeper Artur Boruc to open the scoring.
The visitors were served a significant setback when centre-back Hugo Campagnaro was forced off with a knock in the sixth minute and eventually replaced by Gianluca Grava.
The area vacated by Campagnaro immediately became the focus of the Viola’s attention, and Mattia Cassani came within an inch of equalising when he thrashed Juan Vargas’ cross from the left into the side netting.
Yet, despite this scare and a period of sustained Fiorentina pressure, Walter Mazzarri’s men came within the width of the crossbar of doubling their advantage on 25 minutes.
Lavezzi was the architect once more, whipping over a dangerous outswinging corner which Christian Maggio, who was criminally unmarked six yards out, headed against the woodwork and over, to Delio Rossi’s relief.
Amazingly, the hosts went straight up the other end and emulated their opponents when Cesare Natali powered a Vargas corner kick against the outside of Antonio Rosati’s right-hand post.
Stevan Jovetic then fired narrowly wide with a left-footed effort which swung through a ruck of players and beyond Rosati’s reach, as they continued their ultimately fruitless search for a first-half leveller.
The second period began in a similar manner, with Fiorentina on top, but they failed to press home their territorial advantage and fell further behind 10 minutes into the second half.
There was a feeling of deja vu about the second strike as Hamsik once again took advantage of woeful defending by Cassani, who failed to step up with the defence, to slip Cavani in on goal. ‘El Matador’ was in similarly deadly form, crashing the ball past Boruc at his near post.
While the Polish custodian was perhaps at question for that letting that shot sneak past him, he made up for any perceived mistake when he darted off his line to thwart Lavezzi after the Argentine had weaved through the Fiorentina defence.
The familiar pattern of wave after wave of Viola attacks was soon re-established, but some dogged defending and toothless play in the final third meant the men from Naples held on without too much difficulty and Lavezzi sealed the victory with fine solo goal in stoppage time, breezing past two men before scoring with a fantastic finish from the edge of the box.
Fiorentina will attempt to get back on track when they travel to Bologna on Tuesday, February 21. Napoli, on the other hand, host Chelsea in the first leg of their huge Champions League round of 16 tie later that same night.
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