All eyes were set firmly on the €22 million signing from Manchester City, who was thrust into the starting line-up at the last possible moment, but shortly after broke the deadlock with a close range volley to mark a dominant first half for the Rossoneri.
Though Udinese were toothless during the opening period, they came out with renewed vigour after the interval, and pounced on a shoddy defensive sequence to claw their way back into the game through Giampiero Pinzi early in the second half.
The match seemed destined to end in a draw, but a controversial late penalty call allowed Balotelli to give Milan an important victory with the last kick of the game from 12 yards out, and take them level with city rivals Inter in fourth place.
The feel-good factor surrounding Balotelli’s arrival had San Siro rocking long before kick-off, and perhaps inevitably, matters were whipped into a real frenzy with the news that a late injury to Giampaolo Pazzini forced the big money signing into the starting XI.
And, 35 seconds into his Milan debut, Balotelli came within inches of making the most incredible of starts after sending a shot from the edge of the area agonisingly wide of the far post, with half the fans already celebrating a goal.
The 22-year-old was certainly lively early on, and with 12 minutes gone, threatened in attack again when he slid in M’baye Niang 10 yards out, but his shot was straight at Daniele Padelli.
And Balotelli’s moment would arrive with 25 minutes on the clock. Stephen El Shaarawy did well to squeeze in a cross from the byline, and a deflection took it right into the path of the striker, who volleyed precisely into the bottom corner.
It was a one-man spectacle at San Siro throughout the first half, and shortly before the half-hour mark, Balotelli nearly struck again, this time with a sweetly-hit effort from 20 yards out that brought the very best out of Padelli.
Udinese were fortunate to still be in the game at half-time, but emerged from the interval with a renewed enthusiasm. A glorious ball from Andrea Lazzari was badly skewed over by Antonio Di Natale from close range, but with 55 minutes gone, the visitors would find their leveller.
Milan were caught napping after losing the ball in their own half, and Muriel, with acres of space ahead of him, slid in Pinzi, who bundled his finish past Marco Amelia and into the back of the net.
The Rossoneri had lost some of their edge, and Udinese were well and truly back into game, making matters finely poised as the match moved into the closing stages.
Niang smashed a thunderous effort off the crossbar, and Balotelli forced another admirable save from Padelli, but just when the draw looked a foregone conclusion, an incomprehensible penalty call on a legitimate tackle by Thomas Heurtaux on El Shaarawy allowed Balotelli to win the game from the spot in unforgettable, but controversial circumstances.