The first half of Lazio's trip to the Stadio San Paolo was forgettable; Hugo Campagnaro's wayward header was the only chance of note for hosts Napoli, while the visitors could only muster a Hernanes shot from distance.

The match came to life after the interval, with Lazio goalkeeper Federico Marchetti stealing the show after a number of telling saves to frustrate Napoli.

Ezequiel Lavezzi went close through a curling effort from range and also threatened from Edinson Cavani's flick-on, drawing good stops from Marchetti on both occasions.

Blerim Dzemaili tried to test the Lazio custodian with a vicious free-kick from 25 yards out, but his effort whistled just wide of the target.

The visitors failed to make an impression at the other end, as Djibril Cisse struggled to lead the line without the assistance of an injured Miroslav Klose.

Napoli coach Walter Mazzarri introduced former Lazio man Goran Pandev, on loan from Inter Milan, in an attempt to force the breakthrough.

But Marchetti stood firm as the pressure mounted, superbly keeping out another Lavezzi chance with virtually the last kick of the game.

The draw leaves Lazio first, one point ahead of Udinese, who visit Parma on Sunday.

Third-placed Milan are level with Udinese on 21 points, after they played out a 0-0 draw away to Fiorentina.

A goalkeeper also played a decisive role at the Stadio Artemio Franchi, with Fiorentina's Artur Boruc the hero.

The Poland international produced great saves to keep out Alexandre Pato and Urby Emanuels.

Despite Boruc's efforts, Milan should have found the net.

Clarence Seedorf had a goal harshly ruled out for offside, and the veteran Dutchman also shot wide after being played in by Zlatan Ibrahimovic.

There were goals for Milan's city rivals Inter, as strikes from Thiago Motta and Phillipe Coutinho helped Claudio Ranieri's side record a 2-1 win at home to Cagliari.

A first victory in three league matches sees Inter climb to 16th place, but they are still 12 points off the lead following a disastrous start to their Serie A campaign.