The former Portsmouth pair struck in the second half of a memorable victory for the Rossoneri, who defended with their lives to clinch a priceless first-leg victory
Kevin-Prince Boateng opened the scoring during the second half in controversial circumstances after an apparent handball by Cristian Zapata in the buildup, and Sulley Al Muntari finished off a counter attack for the second goal with nine minutes to go.
Much like last season's 0-0 quarterfinal first leg meeting between the two sides, Barca monopolized possession, but was unable to convert its dominance into goals in the face of a defensive clinic from the Rossoneri, who now look like convincing favorites to advance to the last eight.
In the absence of the cup-tied Mario Balotelli, Massimiliano Allegri called on Giampaolo Pazzini to partner Stephan El Shaarawy up front, while Xavi passed a late fitness test to start in midfield for the visitors.
Early on, Phillipe Mexes was forced to head away a Jordi Alba cross dangerously close to the far post, but the first real opening came when Pazzini’s flick put El Shaarawy in the clear, but a poor first touch allowed Carles Puyol to remove the danger.
As expected, Milan was put under significant pressure by the tiki-taka football of Barcelona, but it was able to stifle the Blaugrana in great numbers, and force them to bide their time with patient passes outside the area.
Mexes was shown a 25th minute yellow card for tripping up Lionel Messi, but the first half passed with little incident as Barca could do little with all its possession, while Milan’s rare forays forward were snuffed out almost as quickly as they began.
The second half progressed in much the same vein as the first with Barca on top, but, just before the hour mark, Milan would take the lead out of nowhere in hotly contested circumstances.
Kevin Constant laid off a free-kick to Riccardo Montolivo, whose shot appeared to cannon off the hand of Zapata. There was no call from the referee, however, and Barca was stunned as Boateng steadied himself to finish from the edge of the box.
Animated protests from the visitors only led to a booking for Gerard Pique, and Barca's frustration continued in front of goal, with Andres Iniesta's fizzing drive from distance about the best it could muster in front of goal.
And with 81 minutes on the clock, Milan's optimism turned to flat out jubilation, when a sweeping move on the break saw M'Baye Niang release El Shaarawy into the area, who in turn teed up the streaming Muntari for a precise volley from inside the box.
The San Siro was rocking with pride and disbelief, and its elation crested as Barca simply could not find a way back into the match in the time that remained, setting up an enticing second-leg at Camp Nou in three weeks, with the Catalans needing to score at least twice.