A last-gasp winner by Julio Cruz gave Inter Milan a 1-0 home victory against Udinese and sent the Nerazzurri back to the Serie A summit.
The Argentina international replaced Ricardo Quaresma shortly after the restart and headed home in stoppage time to put Inter three points clear of Udinese.
AC Milan missed the chance to reclaim top spot from city rivals Inter after being held to a 1-1 draw at Lecce in the evening kick-off.
Milan looked to be heading back to the summit after Ronaldinho fired them in front 11 minutes from time when he converted an Alexandre Pato pass.
Lecce stunned Milan deep into injury-time when Andrea Esposito headed home from close-range to earn them an unlikely point.
Napoli moved a point behind Inter after Daniele Mannini and substitute Marcelo Zalayeta scored midway through each half to claim a 2-0 home win against Sampdoria.
Lazio are up to third after Mauro Zarate's seventh goal of the season set them on course for a 3-0 home win over Siena, with sub Tommaso Rocchi claiming a late double.
Juventus remain sixth following a 2-0 victory at second-bottom Chievo.
Alessandro Del Piero followed up his match-winning double against Real Madrid in midweek with a 40th-minute opener before strike partner Vincenzo Iaquinta sealed Juve's fourth straight league win in the 53rd minute.
Genoa are one place further back after Diego Milito hit a hat-trick against 10-man Reggina.
The visitors lost Andrea Costa to a second yellow card in first-half stoppage time before their resistance was broken by a 54th-minute penalty by Milito.
The Argentina international struck twice more in the last 16 minutes to top the Serie A scorers' chart with nine goals, while Giuseppe Sculli got on the scoresheet in the 81st minute.
Alberto Gilardino has eight league goals after helping Fiorentina remain eighth in the table following a 2-1 win against Atalanta.
Felipe Melo got a 20th-minute opener before Gilardino struck three minutes later, although the Viola were left hanging on after Sergio Floccari converted a 77th-minute penalty.
Mid-table Catania came from behind at home to Cagliari to register their first win in four league games.
Giuseppe Mascara's 36th-minute effort cancelled out a fifth-minute opener by Jeda before Rocco Sabato claimed the winner five minutes from time.