Milan lost 1-0 at home to AS Roma, in fifth place, on Saturday and their lead has been slashed in half.
Lazio and Napoli surged three points behind leaders AC Milan after both sides triumphed in a day of high late drama in Serie A's last Sunday of action before the mid-season break.
Milan lost 1-0 at home to AS Roma, in fifth place, on Saturday and their lead has been slashed in half.
Fourth-placed Juventus could have joined Lazio and Napoli on 33 points had they not been pegged back late on in a 1-1 draw at Chievo.
Serie A top scorer Edinson Cavani rifled in from 25 metres in injury time to give Napoli a 1-0 home win over lowly Lecce and spark wild scenes of celebration at the San Paolo where the victory had looked like it would never come.
Last term's relegation candidates Lazio overcame Udinese 3-2 at home to continue their fairytale season thanks to Cristian Zapata's own goal two minutes from time.
The hosts had taken an early lead through the excellent Hernanes before Udinese equalised just after the break thanks to Alexis Sanchez's header.
Defender Giuseppe Biava hooked in after a corner soon afterwards for Lazio but German Denis levelled again with a stunning header from the edge of the area which wrong-footed goalkeeper Fernando Muslera.
Overhead kick
Despite the win, Lazio coach Edy Reja was unhappy with the attitude of some of his players.
"I am the coach, I make the decisions. There are no phenomenons here," former Napoli boss Reja told Sky.
"Either you understand that the decisions must be accepted for the good of everyone or...you risk everything collapsing."
In another wide open game full of chances, Chievo striker Sergio Pellissier scored in stoppage time to deny 10-man Juventus all three points.
Juve, who beat Lazio last weekend but now lie five behind Milan, went ahead thanks to the in-form Fabio Quagliarella netting an overhead kick on the half hour after Marco Storari had saved home midfielder Michele Marcolini's penalty.
The visitors could have extended their lead despite young midfielder Manuel Giandonato, preferred to the out-of favour Mohamed Sissoko, being sent off early in the second half but the Juve defence was eventually breached after sustained home pressure.
In other games, sixth-placed Palermo were held to a 1-1 draw at bottom side Bari, Catania beat Brescia 1-0 and Parma drew 0-0 with Bologna, whose players have not been paid and could soon walk out for free if a deal to buy the club is not reached.
Sampdoria meet Genoa in the city derby later (19:5 GMT) with the winner able to climb above seventh-placed champions Inter Milan, who were not in league action this weekend because of their victory in Saturday's Club World Cup final.
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