The Uruguayan netted either side of halftime 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, which lost 3-0 to Bologna tonight.
Napoli made a lightning start, taking the lead in the third minute after their Three Tenors combined to carve their way through the Fiorentina defense.
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 right-sided center back Hugo Campagnaro was forced off with a knock in the sixth minute and was replaced by Gianluca Grava.
The Napoli right immediately became the focus of the Viola’s attentions, and Mattia Cassani came within an inch of equalizing 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 in the 25th minute.
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 flag kick against the outside of Antonio Rosati’s right-hand post.
The second period began with Fiorentina on top, but it failed to press home its territorial advantage and fell further behind 10 minutes into the second half.
There was a feeling of déjà vu about the second strike as Hamsik once again took advantage of woeful defending by Cassani, who failed to step up with the defense, to slip Cavani in on goal. And ‘El Matador’ was in similarly deadly form, crashing 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, in the 62nd minute, he darted off his line to thwart Lavezzi after the Argentine had weaved through the Fiorentina defense.
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 placing home with a fantastic finish from the edge of the box.
Fiorentina will attempt to get back on track when it travels to Bologna on Tuesday. Napoli, on the other hand, hosts Chelsea in the first leg of its huge Champions League round of 16 tie later that night.