Milan and Udinese maintain pressure on Juve
Champions Milan, who needed extra-time to beat Novara 2-1 in the Italian Cup in midweek, feared another difficult encounter at their near neighbours after having two efforts cleared off the line in the first half.
However, Zlatan Ibrahimovic emphatically broke the deadlock 12 minutes into the second period following Massimo Ambrosini's assist before Robinho doubled the advantage and Swede Ibrahimovic rounded off the scoring late on.
Juve, threatening to win the scudetto for the first time since their 2006 demotion for match-fixing, confirmed themselves as leaders at the halfway mark of the season with a 2-0 win at Atalanta on Saturday but Milan remain just a point behind.
Surprise contenders Udinese are two points further back in third after a 2-1 home victory over Catania with Pablo Armero and Antonio Di Natale on the scoresheet.
Inter, revived by Claudio Ranieri after a dreadful start to the campaign, beat Lazio 2-1 at the San Siro to leapfrog the Romans into fourth spot.
Tommaso Rocchi gave the visitors the lead but Diego Milito hit back just before the break after a neat interchange with Ricardo Alvarez.
Milito's strike partner Giampaolo Pazzini won it for Inter midway through the second half with a cool finish although there were complaints he was offside from Lazio, who are now fifth ahead of AS Roma after their city rivals thumped Cesena 5-1 on Saturday.
Seventh-placed Napoli, an outside bet for the title for many pundits when the season began, continued their inconsistent Serie A form with a 1-1 draw at lowly Siena where in-form Goran Pandev again saved the Champions League last 16 qualifiers.
Edinson Cavani also missed a penalty for Napoli.
In other results, Palermo overpowered Genoa 5-3, Alberto Paloschi put Chievo 2-0 up but Lecce grabbed a draw while Bologna against Parma and Cagliari against Fiorentina ended in 0-0 stalemates.