JimmyGuitaristPep went for what looked like a 3-3-4, but it was probably a 3-4-3-diamond on paper. He probably watched the first leg and acknowledged they played right into Milan's narrow defence with no width. Clearly wanting to stretch the Milan defence, he went with a front 4, nullifying Milan's spare man in defence. Cuenca was excellent I thought, because he just stayed wide all the time & forced Abate to mark him.
But, Barca were so average for a Camp Nou performance & that showed in there possession stat; just 61% compared to there usual 70-75%. I think Allegri will consider it a missed opportunity because of how average Barca were at home. Overall though, you can't say they didn't deserve to go through.