AC Milan failed to take full advantage of Inter Milan's draw against Palermo on Saturday as it was held to a 1-1 draw by Napoli at the San Siro and missed the opportunity to leapfrog its city rivals to the top of the Serie A table.
Hugo Campagnaro put a lively Napoli ahead in the 13th minute, but Filippo Inzaghi equalised 12 minutes later.
Relegation-battler Atalanta gave its fight for survival a boost with a 3-0 victory over fellow struggler Livorno, which is now bottom of the table.
Simone Padoin set the Bergamasco on their way with the opening goal after 13 minutes and further strikes from Javier Chevanton and Adriano Ferreira Pinto early in the second half sealed matters.
Andrea Masiello scored five minutes from time to grab a 1-1 draw for Bari at home to Parma.
The visitors were fortunate to take a 36th-minute lead after Nicola Belmonte turned the ball into his own net following a cross by Damiano Zenoni but Masiello salvaged the draw.
Lazio secured only its third away win of the season to move four points clear of the relegation zone as Cagliari's woeful run continued.
First-half goals from Tommaso Rocchi and Sergio Floccari clinched a 2-0 triumph for the capital club, which progressed to 29 points from 29 games as a result.
Siena breathed new life into its battle to avoid the drop with a hard-fought 1-0 win over Bologna.
Alberto Malesani's men are now unbeaten in six Serie A games although fourth-bottom Lazio's win at Cagliari means they remain four points from safety after Argentinean Marcelo Larrondo grabbed the only goal for Siena.
Chievo paid the price for its profligacy in front of goal as Maxi Lopez's penalty ensured Catania snatched a 1-1 draw in its relegation six-pointer at the Stadio Marc'Antonio Bentegodi.
The hosts wasted a plethora of chances before Sergio Pellissier eventually gave them the lead in the 64th minute but Lopez scored his third goal in as many games to ensure Catania made the long trip back to Sicily with a point.
Antonio Cassano got the only goal after 77 minutes as Sampdoria climbed above Juventus to fifth in the table with a 1-0 win in the evening game.