The Rossoneri go into the winter break on a high after a two-goal victory against the islanders moved them ahead of Juventus at the league summit
A Francesco Pisano own goal and Zlatan Ibrahimovic strike either side of half-time proved enough for Massimiliano Allegri's men to secure victory against his former club.
And the result ensured that his Milan side would move a point clear of erstwhile table-toppers Juventus, who can, however, retake pole position by defeating third-placed Udinese at Stadio Friuli on Wednesday.
The match had started so brightly for the Sardinians as, with less than two minutes gone, Brazilian loanee Thiago Ribeiro fired an angled drive against the base of Christian Abbiati’s right-hand post after excellent approach play by Andrea Cossu.
However, in what was literally their first attack of the match in the fourth minute, Milan quelled their nerves by taking the lead.
Ibrahimovic dropped deep to pick up possession and then released Robinho with an intelligent through ball. The Brazilian rounded both goalkeeper Michael Agazzi and defender Michele Canini and flashed a low ball across the face of goal, which Pisano turned into his own net under pressure from Antonio Nocerino.
Cagliari refused to allow the goal to dent their confidence, though, and almost restored parity 10 minutes after falling behind when Albin Ekdal forced Abbiati to fly to his right to bat his powerful, swerving drive to safety.
Davide Ballardini’s side continued in this vein for the majority of the first half, with Cossu and Radja Nainngolan driving their team forward. The Belgium international, in particular, seemed intent on drawing his side level, but the accuracy of his shooting failed to match his application as he twice fired wide from the edge of the box.
Milan, while not overly stretched by their opponents, were, on the other hand, not providing much of an attacking threat as they appeared content to go into the break with a narrow lead on a miserably wet Sardinia night.
In fact, the visitors had the look of an exhausted side who were just trying to get through the evening and take top spot before heading for a well-earned winter break.
And they attempted to put the result beyond doubt with an energetic burst at the start of the second period. Alberto Aquilani passed up an excellent opportunity to double his side’s lead in the 50th minute when he waltzed past Canini and fired straight at Agazzi, who blocked with his feet.
But the second goal seemed inevitable as Milan, although still not quite operating at an optimum level, provided more of an attacking threat – and it duly arrived on the hour mark.
Massimo Ambrosini rolled a simple pass to Ibrahimovic, who instantly flicked the ball to Robinho, fastened onto his strike partner’s headed return and nonchalantly lifted the ball over the advancing Agazzi to make it 2-0.
The second goal knocked the stuffing out of Cagliari, and the match petered to a satisfying conclusion for the new league leaders.
Both sides return to action after the winter break on the afternoon of Sunday, January 8. Milan make the short journey north east to face Atalanta, while Cagliari have a second consecutive home fixture, as they host Genoa.