Mario Balotelli scored a brace on his debut, including a controversial late penalty, to secure a precious 2-1 win for AC Milan over Udinese and move the resurgent Rossoneri up to fourth place in Serie A.
Champions Juventus remain top after restoring their three-point lead over Napoli with a 2-1 away win over Chievo.
Lazio's third place is under threat after a 3-2 loss at Genoa which left Vladimir Petkovic's side only three points ahead of Milan and Inter, with Fiorentina, in sixth, a further point behind.
As Inter dropped more points in a shock 3-1 defeat away by Siena, city rivals Milan stole the limelight thanks to a Balotelli double on what was the 22-year-old's debut following his midweek transfer from Manchester City.
Balotelli, a former Inter Milan player, said on Friday he had come to Milan "to help the club win trophies".
After seeing a drive whizz just past the post after 35 seconds, it took him just 25 minutes to show fans his intentions when he latched on to a through ball to smash the ball past Daniele Padelli in the Udinese goal.
Udinese pulled level in the 55th minute when Giampero Pinzi beat Marco Amelia in the Milan goal after being set up by Colombian Luis Muriel.
However, Balotelli made sure of all three points in the fourth minute of injury time when he beat Padelli from the spot after the referee deemed Thomas Heurtaux's challenge on Stephan El Shaarawy to be a foul.
"It's a great feeling to score, but I have to keep on going," Balotelli said. "I'm very happy despite the fact I'm just getting over what has been a difficult period. I didn't play a lot [at City] and I could feel it in my legs. But tonight I was relaxed and I was ready."