Jose Mourinho and Sir Alex Ferguson produced a tactical spectacle for us as usual, so let's break down how this game panned out.
This is a tactical analysis—pure footballing mechanics, no contentious decision debates.
Madrid set up a standard 4-2-3-1 formation with Xabi Alonso and Sami Khedira in a holding pivot. United's was verging on a 4-2-3-1 too, but the wingers were a little deeper and looked more like David Moyes' 4-4-1-1.
Nullifying Cristiano Ronaldo
Much of the focus was on the return of Ronaldo, and Sir Alex Ferguson's hopes of containing him as he did in the first leg took an almighty blow when Phil Jones was ruled out injured.
He opted to utilise Ryan Giggs on the right-hand side, asking for his nous and experience in helping the young Rafael contain the Portuguese forward.
By and large, the combination worked. Ronaldo was frozen out and gradually drifted in toward Gonzalo Higuain's area to find the ball. He had absolutely no joy in the first half.
Real Madrid have star players, but one of their most pivotal performers is Xabi Alonso. He operates as a deep-lying playmaker alongside Khedira and dictates attacks, tempo and movement for his team.
A few teams managed to stop him from playing in the 2011-12 season, and that's what made Jose Mourinho feel it necessary to spend £30 million on Luka Modric—he didn't want to be over-reliant on one player.
Danny Welbeck was deployed in a spoiler role—the same role Mario Mandzukic played to harass Andrea Pirlo at Euro 2012—and stuck to him like glue. It's the role I call "suffoco," and its main purpose is to stop a deep creative player from getting time on the ball.
When off the ball he would chase, when on the ball he made himself open. Going forward, he played as a deep-lying target man. He made himself open to receive the ball and laid it off very well down the channels to release the quick, positive Nani.
He also made some wonderful runs himself, using his agility to spin Alonso and leave him for dust.
The same cannot be said for Alonso, who is too slow to shake a player like Welbeck, as was Pirlo with Mandzukic.
A late fix
It was bizarre that Mourinho opted to send Modric on after his side got the advantage.
Why? Because the red card pulled Manchester United into a 4-4-1 formation—a move which shoved Welbeck to the left-hand side and stopped him pressuring Alonso.
This negated the need for Modric's dynamic skill set and impressive athleticism, but he entered the fray nonetheless.
All of a sudden, Alonso was free. He immediately attempted a direct ball into Higuain's feet in United's box, relishing his freedom.
But Modric was still instrumental. It's his mobility and agility—the type that allows him to skip his marker in a way Alonso is physically unable—that makes him so valuable, and the way he evaded a challenge to fire in the equaliser was simply first-class.
The Red Devils defensive line had no choice but to drop deep, and Madrid's front three interchanged at will to try and open space. That was how the second goal came about, with intelligent movement culminating in a low cross and finish from Cristiano Ronaldo.
Some massive saves from an incredible Diego Lopez were still required to hold out, but los Blancos fly home happy.
Ferguson has become more and more tactically reactive, and tonight was possibly a landmark for him in terms of forward planning.
He planned for Ronaldo, and it worked. He planned for Alonso, and it worked. It's fair to say that until the red card, Madrid's offence was badly stunted and there was no discernible plan.
But with United losing Nani, they had to change shape. It's a testament to how well Welbeck was doing that, as soon as he moved, the game was lost.