Cagliari: Agazzi, Astori, Canini, Agostini, Pisano, Conti, Cossu, Lazzari (Biondini 48), Nainggolan, Nene, Matri (Acquafresca 84).
AC Milan: Abbiati, Thiago Silva, Bonera, Antonini, Abate, Seedorf, Merkel (Cassano 74), Ambrosini, Gattuso (Strasser 58), Robinho, Pato.
Substitute Sidney Strasser netted his first professional goal five minutes from time at Cagliari to move AC Milan provisionally five points clear at the Serie A summit.
The 20-year-old Sierra Leone midfielder, a second-half replacement for Gennaro Gattuso, slotted home a late winner after fine work from new signing Antonio Cassano.
The result extended the Rossoneri's advantage at the top to five points over second-placed Lazio, although third-spotted Napoli can close that gap by winning at Inter Milan this evening.
The league leaders were made hard to work for their win today, with goalkeeper Michael Agazzi pulling off a brilliant fingertip save to keep out an early Robinho effort.
But the visitors did not have it all their own way and nearly fell behind just after the half-hour, when Michele Canini headed a corner against the post for 15th-placed Cagliari.
Milan goalkeeper Christian Abbiati then punched away a bullet 30-yard attempt from Andrea Lazzari as the teams went in at the break goalless.
Abbiati almost gifted the hosts the opener five minutes after the restart with a poor clearance which went straight to Nene, but he wasted his golden opportunity by firing over.
Robinho passed up another chance midway through the second half after latching onto Alexandre Pato's pass, failing to test Agazzi.
Cagliari too were not settling for a point and Abbiati did well two minutes later to keep out a drilled left-footed effort from Alessandro Matri.
But when the deadlock was finally broken it was the visiting fans who were cheering, Strasser beating the offside trap and slotting home from Cassano's pass.