Juventus, who defeated Milan 2-0 at home earlier in the season, are level with the champions on 34 points from 16 matches but with a worse goal difference. Udinese are third on 32 points.
In the remaining round of matches postponed from the opening day of the season because of a players' strike, Lazio stayed fourth on 30 points but continued their poor home form with a goalless draw against mid-table Chievo Verona.
Resurgent Inter Milan came back from a goal down at home to Lecce to claim a 4-1 victory, their fourth league win in a row, and move four points behind Lazio in fifth.
After Inter hit the woodwork four times, Giampaolo Pazzini equalised with his third goal of the season at the near post after 34 minutes.
Substitute Diego Milito gave Inter the lead with a cool 49th-minute finish before Esteban Cambiasso and Ricky Alvarez wrapped things up late on.
Napoli reacted to Sunday's home defeat by Roma with a spectacular first half display to blow away Genoa and remain joint sixth on 24 points.
The absence of Argentine forward Ezequiel Lavezzi was hardly noticed as Edinson Cavani grabbed a brace with Marek Hamsik and Goran Pandev also scoring in a devastating opening period.
Uruguayan midfielder Walter Gargano and Colombian Zuniga added more goals after the break in the 6-1 win.
AS Roma's good away form continued at Bologna as first half goals from Rodrigo Taddei and Pablo Osvaldo gave Luis Enrique's side an easy 2-0 win to keep pace with Napoli.
A goal five minutes from time by Andrea Catellani earned Catania a 3-3 draw at Parma who had led 3-1 up.
Palermo's new coach Bortolo Mutti saw a debut victory slip from his hands as Novara came back from two goals down to draw 2-2 with Marco Rigoni equalising six minutes from time.
Atalanta, whose name was once again mentioned in connection to a match-fixing scandal this week, cheered up home fans with a convincing 4-1 win over lowly Cesena, climbing to 11th.
In freezing conditions in Udine, Juventus had the best chances of a tight game with Claudio Marchisio shooting just wide 10 minutes before the break and substitute Fabio Quagliarella going close with two snapshots late on as Juve headed for the winter break still unbeaten.
Gianluigi Buffon blocked Udinese's best chance from Chilean winger Mauricio Isla early on with the draw ending Udinese's 100 percent home record.
Juventus coach Antonio Conte cut a contented figure.
"There are draws and draws and we've now played against five of the top six sides away from home," he told Italy Sky Sport channel. "We're unbeaten and I'm happy.
"If someone had told me in July that we would finish the year without losing I would have thought he was mad.
"You need to prepa
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