Giacomo Bonaventura produced a stunning strike to level the match for Milan, which was on the back foot for much of the contest.
Milan dropped points for the second game in succession, but was grateful to Giacomo Bonaventura for rescuing a 1-1 draw at Cagliari.
Filippo Inzaghi's side - denied victory in Serie A by Fiorentina at the weekend - was second best for long periods as it claimed a point at Stadio Sant'Elia on Wednesday.
Zdenek Zeman's Cagliari missed out on a Milan double, having beaten Inter 4-1 earlier in the season, after Victor Ibarbo's deserved first-half opener was canceled out by Bonaventura's sublime 30-yard lob.
The host side steadied itself in the second period and looked the more likely to win the game as Daniele Conti struck the post with a well-struck free kick.
Milan was forced to defend desperately for long stretches, but remains unbeaten on its travels in Serie A this term, while Cagliari's wait for a first home success goes on.
The hosts entered the game fresh from a 4-0 thrashing of Empoli on Saturday, and their excellent start to the game looked like being rewarded as early as the fourth minute.
Ibarbo had a gaping goal in front of him after Danilo Avelar squared to take Christian Abbiati out of the game, having collected Conti's perfect through ball. However, Adil Rami reacted and produced a sensational sliding block to somehow keep the scores level.
Ibarbo's pace and power had Milan on the back foot throughout the opening exchanges and he did make the breakthrough on 24 minutes.
The Colombian spotted a gap between Rami and Mattia De Sciglio, and darted into the space to beat Abbiati to Marco Sau's inviting, clipped cross from the left and head into the net from eight yards.
Milan then drew level out of nothing after 34 minutes. Bonaventura received a throw-in 30 yards from goal under no pressure and had time to spot Alessio Cragno off his line before executing a perfect curled lob into the top corner, stunning the stadium into silence.
Despite conceding, the hosts were not to be discouraged and began the second half in much the same manner as they had the first.
Conti whipped in a dangerous low cross from the right 10 minutes after the break and only a desperate lunge from Ignazio Abate took the ball off the toe of an on-rushing Andrea Cossu, denying a certain goal.
Substitute Diego Farias should have won it for Cagliari in the final minute of regulation time, but fired straight at Abbiati from seven yards after being picked out by Sau.