Goals from Kevin-Prince Boateng and Sulley Muntari secured AC Milan a deserved 2-0 win in the first leg of their Champions League last-16 tie against Barcelona to leave the Liga giants with a mountain to climb.
Boateng broke the deadlock on 56 minutes at San Siro with a smart finish on the turn, as Barca appealed in vain for a handball in the build-up.
And Milan claimed a second with nine minutes left on the clock when Stephan El Shaarawy helped a ball onto Muntari, who fired past goalkeeper Victor Valdes.
The home side continued to keep Barca at bay to clinch what could prove to be a decisive result ahead of the second leg at Camp Nou on March 12.
Elsewhere, Jermaine Jones' strike in the last minute of the first half gave Schalke a slight advantage as they drew 1-1 at Galatasaray .
Jones calmly slotted home after Jefferson Farfan had squared the ball to him to give the German side a vital draw at the Turk Telekom Arena, although Schalke's goalscorer will miss the second leg after picking up a booking.
Burak Yilmaz had earlier put Gala in front with a piece of individual brilliance but they could not extend their lead in a breathtaking first-half in which both teams failed to convert several glorious opportunities.
The second half was decidedly less open, although Yilmaz nearly gave the hosts a slender lead heading into the second leg but could only fire wide of the target.