minutes, but Edinson Cavani's superb bullet header from Juan Zuniga's deep cross did not cross the line when it rebounded off the Lazio crossbar.
Lazio began with a flourish after the restart and Floccari again had the ball in the net, only to be ruled offside after he nodded home Andre Dias's shot from close range.
Napoli were growing increasingly frustrated as they fought for an equaliser in the face of a disciplined and alert Lazio defence.
Mazzarri eventually sent on Omar El Kaddouri in place of Giandomenico Mesto and the Moroccan saw his long-range effort parried by Marchetti.
After Napoli midfielder Goran Pandev was clattered to the ground by Stefan Radu, earning the Lazio man a yellow card, Gokhan Inler saw a long-range drive force Marchetti into action again.
However Lazio continued to dominate and spurned the chance to double their lead when Bosnian defender Senad Lulic lobbed the onrushing De Sanctis only for Campagnaro to rush back and clear the danger.
After Pandev's looping header from the edge of the area was collected easily by Marchetti, Napoli looked to have run out of steam.
But from a corner on the right, unmarked Campagnaro rose to smash a superb volley past the rooted Lazio 'keeper from less than 10 yards out to pull Napoli level.
An alert Marchetti then parried Pandev's angled strike in the final minute of time, however Lazio were not finished.
Floccari had the chance to seal it for Lazio in injury time only to send his bullet header spinning off the crossbar as De Sanctis looked on.
Candreva, charging down the right, then saw his angled, deflected drive force a diving save from the Napoli keeper.
Lazio coach Petkovic was left to lament: "It was a great game by the lads, we created so many scoring chances but we had to be more clinical." (AFP) PM
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