Nani's dismissal obviously had a bearing on the course of the tie but questions were still asked about how the Reds' 10 men were unable to hold out for longer against a side that went full throttle after the introduction of Luka Modric as a substitute.
The manager has his own theory on what went wrong, apart from referee Cuneyt Cakir's controversial decision, but he finds it difficult to blame his players, who finished the game strongly despite the numerical disadvantage.
Sir Alex said on Countdown to Kick-Off: "Let's be honest, it was hard to take, when you think about all the work that was done in terms of preparation for both legs. The players' performance level was fantastic. The support was unbelievable. We didn't deserve that and it's a fact.
"You just couldn't believe it [the red card]. Quite astonishing. I think, in general, we know it was the wrong decision. I think, after looking at the game again a few times, the players were shocked.
"They couldn't recover from it until we lost the second goal and then they galvanised themselves and were fantastic in the last 15 minutes of the match. They were absolutely brilliant and we could've scored five goals. It was a fantastic performance by the players with 10 men but, in that period after the sending off, they played in shock.
"Knowing we'd had a bad decision against us again, we couldn't get going for 10 minutes. Their