Massimiliano Allegri masterminded an epic defensive stand to beat Barcelona, 2-0, at the San Siro on Wednesday night. AC Milan were huge underdogs in their UEFA Champions League Round of 16 matchup, but defied the odds to take a two-goal advantage and a clean sheet to the Nou Camp in three weeks' time.
They were rigid, disciplined and tactically switched on for the full 90 minutes, so let's break down what was more than just "parking the bus."
Barcelona set up their customary 4-3-3-cum-2-3-5 in all-out-attack mode, while the Rossoneri mirrored their formation but utilised a far more defensive, counterattacking model.
To break Milan's performance down, I'm going to split it into three phases but identify one constant, as throughout the 90 minutes, Allegri juggled things ever so subtly.
Phase 1: Initiate protocol Chelsea
There's no escaping how defensive Milan were for the opening 57 minutes.
Philippe Mexes and Cristian Zapata sat deep and kept their full-backs on a restricted tether, so the Rossoneri were playing with a very, very flat back four.
Massimo Ambrosini, Riccardo Montolivo and Sulley Muntari played as a triple midfield anchor (something I've not seen to this extent before), and their average position was just three-to-five yards in front of the defensive line.
To add to that defensive seven, Stephan El Shaarawy and Kevin-Prince Boateng tucked back in on the wing to form a true five, and even Giampaolo Pazzini was goal-side of Sergio Busquets most of the time.
Milan simply set up shop and asked the question—can you pass your way through us in this congested area?
The answer was no; certain areas of the pitch were open for exploitation, but Barca simply didn't exercise those options enough. The channel in between Mexes and left-back Kevin Constant was often open and Pedro clearly wanted to burst through it, but the pass never came.
The surprising tactic: Xavi was man-marked
All this talk about man-marking Lionel Messi before the game—what were we thinking?
By man-mark we don't mean stick to him, but Allegri pulled a subtle surprise out of the hat by telling Muntari to stay approximate to Xavi, and the Ghanaian's position was almost constantly relative to the Spaniard's location.
This saw Milan venture out in a very lopsided look, with Muntari sometimes horizontal with Pazzini as he followed him toward the halfway line, but sometimes tucked in level with the deepest midfielder, Ambrosini.
This constant changing of position (according to where Xavi was, and he roamed all over the place) made El Shaarawy's positional play and awareness of Dani Alves all the more important.
Muntari typically stayed 10 yards away from Xavi at all times and never engaged him head-on for a tackle, but simply opened and closed the space in front of the playmaker according to where Milan were willing to let Barca have the ball.
He'll take the headlines for his goal, but the silent job he did here was first-class.
Phase 2: We've got the goal, now don't sink too deep
A crime many teams commit when playing against superior opposition is, after scoring a goal, sinking incredibly deep and trying to protect their lead.
Well, for Milan to drop even deeper was borderline impossible, but rather than resume what they were doing, Allegri's troops made a conscious effort to move up the pitch.
This opened the gap between the defensive and midfield lines from around five yards to 10, and made both wingers more effective attacking options.
This wasn't without risk, but Messi had an ineffectual game and Jordi Roura brought Alexis Sanchez on to play in a hybrid No. 10 position. Mexes and Zapata went from having no one to mark to sharing one player between them, and it was still so congested that all La Blaugrana could do was deliver it aerially to the Chilean and hope he could bring it down.
Phase 3: Forcing the issue, and rightly so
Nothing highlighted the immense understanding Milan's midfield have of each other better than the final 10 minutes of this match.
Even with a two-goal lead, Barca were still just one strike from heavily damaging the Rossoneri's chances in this two-legged tie.
When teams play Barca, they sit back. That's not a mistake—men behind the ball clearly works—but what often happens is that Xavi slows the pace of the game down so much that the opposition come to a standstill.
That's when they strike.
When you face up to this side, the players you can see in your field of vision aren't the ones you need to worry about; it's the one you missed flying down the right-hand side at full speed to meet a through ball from nothing.
The change-of-pace abilities this side have are incredible, and it's no wonder they score so many late goals against tired defences. To stop this from happening, Milan were determined to get in their faces right till the final whistle.
Under no circumstances did these guys stop motoring around. They were constantly on the move, looking sharp and ready for the ball to come their way.
As Xavi and Busquets dropped in to collect the ball, the nearest Milan winger would sprint toward the ball-player to put them under pressure and force them to act. As Barca looked to pass into the area this winger just left, the outside midfielder in the triple anchor sped across to cover the gap. Try the other side, exactly the same thing happened.
It was a simple case of fill the hole your colleague left, and it's something many mess up. This kept the tempo high, the energy high, Milan off their heels and stopped fatigue from setting in.
But most importantly, it didn't allow Barca to explode through a gap and create something special. If anyone dictated the tempo of this match, it was the Rossoneri, not La Blaugrana.
This wasn't just parking the bus, this was defensive perfection.
Xavi was man-marked from a distance, Muntari's position silently dictated the shape of Milan's team and Ambrosini played like a warrior inside the "D" of his side's box.
This XI played incisive, counterattacking football and, but for Muntari's sloppy first half on the ball, could well have had even more unthinkable joy.
Well played, Allegri.