Atletico Madrid made a smooth transition from "dark horse contender" to legitimate threat in this year's UEFA Champions League on Wednesday, dispatching Barcelona 1-0 (2-1 aggregate) at the Vicente Calderon.
In a charged atmosphere draped with Rojiblanco flags, scarves and shirts, Koke stabbed the hosts into the lead after Adrian had hit the bar with a stinging, angled shot.
David Villa then hit the woodwork twice and was denied a clear penalty, while both Gabi and Cristian Rodriguez hit tame efforts straight at Jose Manuel Pinto when one vs. one with the stand-in.
All this without 33-goal Diego Costa—the man whom so often rides to their rescue with a solitary, deciding goal—and Turkish speedster Arda Turan, essential to their quick-break, counterattacking philosophy.
But with Atleti there is no grumbling, no kicking their feet in the sand; they got on with it, plain and simple, and plugged viable replacements into a well-oiled, nearly unbeatable system.
And that's the key to Diego Simeone's success this season, the reason why los Colchoneros will be feared in the semifinal draw: his system has proven to be mightily effective—even when using some relatively modest players.
Real Madrid have shown areas of weakness in La Liga and Europe, Bayern Munich can seemingly only turn it on when they're a goal down and Chelsea still lack a striker who can make the difference no matter what Demba Ba says.
Atletico Madrid present a horror tactical matchup for any side who struggles to break down deep defensive systems set out in low-blocks. Bayern, Real and Chelsea could all fall should they draw the perceived "dark horses."
Simeone's narrow, hardworking 4-4-2 is easily the most frustrating, stubborn formation in world football right now. They sit deep, pack the middle, man-mark the wide men and tell the opponents' full-backs: "cross it in—if you dare."
Diego Godin regularly finishes matches having won 100 percent of his aerial duels, as per WhoScored, and teams playing with a lone striker find it impossible to overcome both he and Miranda in the centre.
Gabi stitches the lines together to ensure the distances between are equal, and the formation expands and shrinks seamlessly like an accordion all game long.
Costa plays a sideline-to-sideline target man role, occupying two defenders, drifting wide and giving his midfield runners a chance to join him in attack. Bar perhaps Robert Lewandowski, there are no better strikers in football at this function.
The aggression, passion and energy on display in every game is near-impossible to replicate, and with the belief coursing through the players' veins, Simeone's system moves from strength to strength.
Atletico Madrid sit top of La Liga with six games to go and are now looking forward to a Champions League semifinal. Unlike Chelsea, who are easier to game-plan for, this side represents the real stubborn challenge left in the draw.