Many in the game had written them off, but with the sort of attacking flair and creativity that's become a trademark of their success, Barcelona cruised past Milan tonight 4-0 with a ruthless, terrifyingly efficient display.
A wonderful, curling finish from Lionel Messi gave the hosts the lead following a well worked move with Andres Iniesta at the edge of the area after just five minutes, and he doubled their advantage with an impressive strike shortly before half-time, mercilessly punishing Milan for their carelessness in possession, a feature all too common tonight in what was a nervy display.
Villa was to edge the Catalan side ahead on aggregate with his goal 10 minutes after the break, and in the dying stages of the 90, Jordi Alba put the tie beyond doubt, adding the finishing touch to a stunning move which had started, strangely enough, with Robinho gifting them possession from a set piece.
In many ways, it was a perfect display from Barcelona—incisive, ingenious and lethal, in short, everything which they weren't in the first leg.
But it could all have been so different.
One incident in the first half where the footballing gods smiled in favour of the home side was to have an immeasurable impact on the outcome of the tie as a whole.
With 38 minutes on the clock and Barcelona still leading by just the single goal, M'Baye Niang latched onto a loose ball, managed to get away from Javier Mascherano and bore down on goal. An entire stadium—not to mention the millions watching around the world—held its breath as he steadied himself to shoot. Although he managed to place his right-footed effort out of the reach of Victor Valdes, he could only watch as the ball struck the keeper's right upright instead of nestling in the corner of the net.
It was a matter of inches. A few to the left, and Milan would have been celebrating a goal which would have put them in a commanding position in the tie.
For all the difference it made, it may as well have been a couple of thousand miles.
Had Milan leveled the game at that point, the entire complexion of the game would have changed. At 1-1 going into the interval, and with Milan having managed to obtain that priceless away goal, Barcelona would have been faced with a far more arduous task. Although they were to go on to score a total of four on the night, it might well have been hard for them to see such an outcome when 3-1 down on aggregate with just 45 minutes of the tie left to be played.
The goal would have undoubtedly given Milan a renewed sense of confidence, vital for a team who looked nervous—and at times frightened—in such an arena and against such irresistible opposition. Momentum might just have swung in their favour, and it would certainly have gone a long way to knocking the wind out of a Barcelona side who were moving the ball around with such ease and vigour that it seemed at times impossible to find a way to stop them.
Coming out at the start of the second half with the game tied at 1-1—and with the away goal meaning they were effectively three goals better off—Milan would then perhaps have been able to slow the game down a little, dictate possession and to frustrate Barca in their hunt for a goal to get them back in the tie.
Now of course, this isn't pinning the blame on M'Baye Niang by any stretch. He did well to get himself into such a good position to take the shot in the first place. While he perhaps took a touch too many to steady himself and scuffed his shot ever so slightly which caused it to hit the post, he's still only just 18 years old and has precious little experience of playing at this sort of level.
Contrast that with someone like Massimo Ambrosini, who, despite having a wealth of Champions League experience to his name, looked woefully inept in the middle of the park, and was guilty on all too many occasions of giving the ball straight to the opposition. Boateng and El Shaarawy did little in an attacking sense, even if they did suffer from a serious lack of quality service and the defence were panicky and unsettled right from kickoff.
Milan didn't lose tonight's game, and the tie overall, because of Niang's miss—they lost the tie because of a frail, listless display which made it all too easy for Barcelona to play the type of football they excel at when given the opportunity.
For Milan fans though, images of the young French striker's miss will be almost impossible to get out of their minds, and they might never quite be able to stop themselves from wondering about how very different it could have been had he scored.
So often football comes down to the smallest of margins.
4-2 was the aggregate score between the sides, but in so many ways, the really telling figure was how many centimetres to the left M'Baye Niang skewed his shot.