|Motta, above, and Philippe Coutinho scored in a six-minute period of the second half to give Inter the edge [EPA]
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 in Italy’s Serie A.
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 lead if they win tomorrow.
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.
Thiago Motta scored a controversial opener before Coutinho secured the points although Joaquin Larrivey scored a late goal for the visitors to give Inter some nervy moments at the death.
The victory was crucial for Claudio Ranieri's players who have struggled at the bottom of the table all season.
Calgiari have now lost their last three and failed to win in six scudetto matches.
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 after Ricardo Alvarez, who had replaced Zarate at the break, swung over a free-kick from the left which Pazzini flicked on for 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 smiling," said Ranieri in reference to Inter's feeling they have been harshly treated with penalties this season.
"It was offside but maybe the linesman didn't see Pazzini's touch."
Brazilian star Coutinho finished off a swift attacking move with a daisy cutter from 17 yards that crept just inside the near post.
Cagliari had a goal from 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's best chance of the opening period saw Hugo Campagnaro head Ezequiel Lavezzi's free-kick over the bar.
Lavezzi was Lazio's tormentor in chief after the restart as his curled effort forced a diving save from Federico Marchetti.
From the resulting corner Lavezzi was left totally unmarked at the back post but his acrobatic volley flew over.
Marchetti also made an instinctive block to stop Edinson Cavani's left-foot volley and in injury time plunged to his left to keep out Lavezzi's strike.
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.
Alberto Aquilani headed Robinho's cross just over for the visitors while Alberto Gilardino blazed Fiorentina's best chance well over on the volley.
Pato almost snatched victory for Milan on his return from injury as a substitute but Artur Boruc tipped his low shot onto the post.