After Milan had steamrolled relegation-haunted Sampdoria 3-0 on Saturday, second-placed Napoli proceeded to go down 2-1 at home to Udinese on Sunday.
Coupled with defending champions Inter Milan's shock 2-0 reverse at struggling Parma on Saturday, Milan now have a six-point cushion over Napoli with only five matches remaining.
Inter are two points further back and hanging on for dear life to the third automatic Champions League qualifying spot, with Lazio in line for the qualifying round slot three points adrift of the nerazzurri after an emphatic 4-1 win at Catania.
Even better for Lazio fans, their city rivals Roma lost 3-2 at home to Palermo to leave the losers seven points off fourth place with little hope of seeing Champions League football next season.
Udinese are a solitary point behind Lazio after their fine win in Napoli, achieved in the absence of injured stars Antonio Di Natale and Alexis Sanchez.
Gokhan Inler gave Udinese the lead with a superb strike in the 55th minute, with former Napoli forward German Denis doubling their lead on the counter-attack minutes later.
Walter Mazzarri's Neapolitans aided their own downfall with Edinson Cavani's missed penalty on 88 minutes before Giuseppe Mascara notched a late consolation deep into injury-time.
Lazio stayed in touch with Inter after Hernanes put them ahead on 40 minutes for his second goal in two games.
Ezequiel Schelotto levelled straight after the break but further goals from Stefano Mauri, Sergio Floccari and Mauro Zarate -- who also provided two assists -- underlined the visitors' superiority.
Juventus are a point behind Roma in seventh after the Old Lady could only draw 0-0 at mid-table Fiorentina, ending a run of three straight victories.
In the race to beat the drop, 17th-placed Cesena leapfrogged Sampdoria after a 1-0 win over Bari courtesy of a goal from Albanian Erjon Bogdani.
Brescia, 19th, are on the brink after a 3-0 loss at Genoa left them four points off safety.
Lecce are fifth-bottom, one point ahead of Cesena, after recovering from 3-1 down to draw 3-3 with Cagliari, with a Daniele Corvia goal deep into stoppage time saving their bacon.
Angry Sampdoria supporters, whose team have now slid into the bottom three, attacked the team coach on its return from their loss at Milan, which deepened their very real relegation worries.
The masked supporters hurled stones and struck the bus with sticks on its return to the team hotel in Genoa early on Sunday morning, according to press reports, breaking the windscreen.
The supporters have issued death threats to the squad should they be relegated.
"No result, even a really bad one, can justify such behaviour," the club said in a statement.
Clarence Seedorf, former Sampdoria star Antonio Cassano and Robinho were the men on target for the rossoneri, who were not unduly troubled by the absence through suspension of Sweden striker Zlatan Ibrahimovic.
Inter, already smarting from their Champions League exit at the hands of Schalke, saw Sebastian Giovinco and Amauri bag Parma's goals in their loss, which Inter coach Leonardo blamed on fatigue.
"We need points -- eight behind, that's a lot," said Leonardo.
"Five behind, you can still believe, but the problem is getting over the tiredness."
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