Troubled Inter Milan earned only their third league win of the season on Saturday as they beat Cagliari 2-1 at the San Siro while Lazio went top with a 0-0 draw at Napoli.
Udinese can return to the summit if they match or better Lazio's result away to Parma while Juventus, who will host Palermo, could also claim the Serie A lead if they win.
AC Milan failed to make the most of Lazio's slip as they were held to a 0-0 draw at Fiorentina, leaving them a point behind the Romans.
Inter's win left the 2010 Champions League winners still down in 16th position ahead of Sunday's games and only three points above the relegation zone.
The victory was crucial for Claudio Ranieri's players who have struggled at the bottom of the table all season.
Ranieri felt they needed the first goal to come alive.
"We need to raise our tempo because once we got off the mark we had more spark," he said..
"There are things to look but that's ok."
Inter twice hit the woodwork in the first half when Cagliari goalkeeper Michael Agazzi tipped efforts from Giampaolo Pazzini and Mauro Zarate onto the bar.
Inter broke the deadlock nine minutes into the second half when Pazzini flicked on a Ricardo Alvarez free-kick for Thiago Motta to bundle home, although he was both offside and seemed to handle the ball.
"It's true, our first goal was offside but for once we're smilling," said Ranieri.
"It was offside but maybe the linesman didn't see Pazzini's touch."
Brazilian starlet Coutinho scored the second on the hour with a daisy cutter from 17 yards.
Cagliari had a goal from Joaquin Larrivey ruled out for offside and Davide Ballardini, the Sardinians' third coach already this season, felt the decisions that went against his side were symptomatic of supposed favouritism towards the big teams.
"At the San Siro the one consistency is that certain clear situations become shrouded in doubt and when there is doubt the refereeing decisions favour the strongest," he said.
"This has already happened in the past when the visitors have been penalised."
Larrivey was well onside a minute from time, though, when he turned home Radja Nainggolan's shot from the left.
Lazio needed a backs to the wall effort at times to hold onto a point in Naples.
Napoli wasted a host of glorious chances as Lazio goalkeeper Federico Marchetti had a stormer, twice pluinging to his left to keep out Ezequiel Lavezzi efforts and making an instinctive block from Edison Cavani.
Lavezzi wasted an open goal as he blazed an acrobatic volley over while Cavani had the ball in the net only to see it ruled out for offside.
Such was Napoli's domination that coach Walter Mazzarri seemed confused after the game.
"I've just told the players that for me we won 4-0, we played a phenomenal match," he said.
"We did the possible and the impossible but the ball didn't want to go in. I hope we'll win when we don't deserve it."
The champions dominated in Florence but their run of five straight league wins still came to an end.
Milan did have the ball in the net in the first half but Clarence Seedorf's close range volley from Zlatan Ibrahimovic's dink was controversially ruled out for offside.
Pato almost snatched victory for Milan on his return from injury as a substitute but Artur Boruc tipped his low shot onto the post before somehow also blocking Urby Emanuelson's follow-up.
Milan coach Massimiliano Allegri was happy with his charges, particularly Pato.
"We played well, we put some crosses into the box in the first half, we had a valid goal disallowed, there were two dubious episodes in the game," he said.
"It's a shame because the way we played we could have won, their goalkeeper made important saves from Pato and Emanuelson.
"Pato did well, he hit the post and created several chances, he had a good 25 minutes."