Leaders Inter Milan failed to win in Serie A for the first time in nine matches when they were held to a 0-0 draw at Udinese on Sunday.
The unbeaten champions had Brazilian winger Cesar sent off for two quick bookings after just 21 minutes but still had the better chances to beat fifth-placed Udinese with Julio Cruz and strike partner Zlatan Ibrahimovic going close.
Inter's lead from last week has been cut to five from seven points after second-placed AS Roma won 1-0 at home to Palermo on Saturday. Juventus, 13 points behind Inter in third, visit Livorno in the late game.
Brazilian striker Pato scored twice in the second half to give AC Milan a 2-0 win over 10-man Genoa and lift the stuttering European champions to seventh.
The 18-year-old has now scored three in his first four games for the club and three in two at the San Siro where Milan had failed to win against Italian opposition before his arrival at the start of the month.
Milan again lacked bite in the first half and were wasteful in the second before Pato nodded in after Clarence Seedorf's header across goal on 69 minutes.
Genoa goalkeeper Rubinho was then dismissed for handling outside the box when he denied the onrushing Pato, who was playing upfront alone with Ronaldo again out injured.
He grabbed his second eight minutes from time when he walked the ball into the net to boost Milan, who have two games in hand including Wednesday's trip to Reggina.
Fourth-placed Fiorentina moved level on points with Juventus after Adrian Mutu's 13th league goal of the season set up a 2-0 victory at second bottom Empoli.
Basement side Cagliari are now just three adrift of Empoli after a stunning late comeback against Napoli. Alessandro Matri and Daniele Conti both scored late in stoppage time to record a 2-1 win, their first since Sept 30.
Substitute Rolando Bianchi had a debut to forget when he was sent off after five minutes of Lazio's 0-0 draw at Torino.