Ibrahima on the break but Valdes collects and there's the final whistle. The champions are finally beaten. Their lead at the top is now just two points and Atletico have fully deserved the points here.
Substitution Sergio Agüero Ibrahima
One minute to go, Atleti in possession.
Atleti make another change as the clock shows three minutes of added time to be played. This win will surely be a massive confidence boost for Atletico as they look to return to their rightful position in the table.
MESSI!!!!!!!!! He fires wide from 20 yards after a surging run through the middle.
Ibra booked for trying to flick the ball away from De Gea as he kicked it out of his hands.
Yellow Card Zlatan Ibrahimovic
Barca are staring down the barrel of their first league defeat of the season now with a little over three minutes remaining. Jose Antonio Reyes walks off to a standing ovation, how times have changed at the Calderon. Valera comes in.
Substitution Reyes Juan Valera
Barca have a free kick 30 yards out, Iniesta fouled. Shambolic waste there and Puyol trots all the way back as Atleti stifle Barca once again.
Ujfalusi climbs over Ibrahimovic to concede a corner but Irba is flagged offside. It'll be a free-kick to Atleti.
Substitution Diego Forlán Jurado
It looks like Jurado is going to come in for the final ten minutes.
Yellow Card Carles Puyol
Bojan puts Ibra in possession inside the box but the Colombian is there again, to concede a corner.
Xavi is coming off with Bojan coming in. It's been his poorest display in a Barca shirt in a long time.
Substitution Xavi Bojan Krkic
This time he did opt to go over the wall but it didn't come down in time. Goal kick.
Yellow Card Busquets
Busquets booked for hand ball, 25 yards out, just left of centre. it's just outside the D and Simao fancies this...
Maxwell fends Reyes off with an arm and that is a free kick. Simao takes it and Ujfalusi's back post effort is deflected out for a corner.
Sloppy pass from Busquets, expecting Bartra to chase forward and it rolls out for a throw-in. It's been an out of sorts performance from the champions and that pass typifies their display.
Tiago is finally booked after upending Busquets and then Bartra a moment later.
Yellow Card Tiago
Atletico are working extremely hard, not allowing Barca a yard of space and they force them back into their own third of the field. The champions finding it difficult to impose their passing game.
Yellow Card Maxwell
Excellent tackle from Puyol after Aguero appeared to have stolen through on goal. The challenge was perfectly timed as the Argentinian was just about to pull the trigger.
Messi and Xavi link up down the right and Pedro makes a great run across from the left but his touch lets him down as Xavi tries to find him inside the box.
Substitution Jeffrén Suárez Bartra
Iniesta threads a fantastic ball through to Ibrahimovic on the edge of the box. He could have turned into space and struck it goalwards but opted to turn inside the defender and got unstuck as Perea cleared.
Yellow Card Simão
Great run from Aguero, he looked to have run himself into a cul de sac but turned past Puyol and fired at Valdes from a tight angle. The keeper saved well, conceding a corner.
Chance for Barca, Iniesta inside the box, is touch lets him down and De Gea gets there, the ball spills across the box and Ibra's effort is blocked on the line. Messi follows Xavi's cross in but De Gea gets there once more.
Ibrahimovic barges forward, latching onto Iniesta's pass but Perea makes a brilliant block on the edgoe of the box, conceding a corner.
It was actually a wider angle than Simao's effort and Xavi opted to pass to Iniesta on the far post but Antonio Lopez read it and headed clear.
Messi felled by Tiago, in the same spot Simao scored from in the first half. Can Barca replicate the Portuguese stars effort. It'll be Xavi...
Barca get caught trying to play the ball out of defence and at the second attempt Xavi wins a free kick.
Great control from Ibrahimovic but he'd strayed offside from Maxwell's long ball.
Iniesta and Ibrahimovic get us back underway here. Can Barca make amends in the second half or will Atleti end a great week on a high note.
Atleti are back on the field, struggling to stay warm as they wait for Barca, here come the men in yellow now...
HALF-TIME! There's the half-time whistle, Barca trail by a goal. It could be worse however, had Aguero been more clinical in front of goal. Keita's injury is another blow but the champions have also had chances, it's all to play for after the break.
Messi wins a corner off Simao and is free 16 yards out to receive the deep corner. He fashions a yard of space but his shot is saved by De Gea.
Jeffren gets the better of Simao this time and wins a free kick. Atletico come again and Aguero is fed in by Ujfalusi who makes a surging burst forward. The Czech looks for a return inside the box but Aguero shoots, it's a poor effort, the ball was going away from goal and Valdes clutches that with ease.
Xavi with a corner for Barca, great work from Iniesta to win it but Ibra concedes a free-kick pulling Perea's shirt as Puyol tests De Gea with a downward header.
Simao gets the better of Jeffren aerially and the stand-in full back doesn't get close enough to his man but Puyol is there to assist.
Barca fail to find a way through Atleti's well organised defence and eventually Iniesta tries a clever ball over the top to Ibra, it's a little heavy and runs out for a goal kick.
Jeffren caught out as Forlan slips in behind him but he can't control it concedes a throw-in stopping it going out for a goal kick.
The pace is by no means frantic but it's still fairly open and Simao ponces on a mistake from Puyol, playing in Aguero but the Argentine tries to be a little too clever, trying to lob Valdes from an impossible angle. He had little to aim at there.
De Gea again gets down smartly to save from Messi. Fine save.
Ibrahimovic shows great footwork to fashion a yard of space with Ujfalusi in close attendance. He comes in off the left and from 15 yards smashes goalwards but De Gea does well with an outstretched save.
The Argentinian recovers well and wins a corner, which Ibrahimovic heads goalwards. It was on target but it didn't have enough power to test De Gea.
Messi beats two players but tries to do a little too much, he had options outside and should have looked for Pedro who was in space. Atleti clear through Dominguez.
Another free kick out wide for Atletico and a deflected effort from Tiago came off Puyol but Valdes gets down smartly to save.
Yellow Card Jeffrén Suárez
From a corner, Milito rose highest but couldn't direct his header on target it fell to Ibrahimovic all alone on the back post. Luis Perea had come off the post to anticipate the header down leaving the tall Swede alone 5 yards out and he smashed a volley past De Gea.
Goal Zlatan Ibrahimovic
Pedro wins another corner off Ujfalusi, IBRA SCORES! 2-1.
Decent move from Barca involving Iniesta and Pedro down the left, Ibrahimovic tried to meet the cross at the near post but Dominguez concedes the corner.
The Portuguese winger curled it round the wall into the far side of the net. Valdes had skipped across expecting him to go over the wall and couldn't get back across in time. The champions in trouble now, time to show their championship credentials.
The champions are struggling for their familiar fluidity and the Caalderon has not been a happy hunting ground with three of their last four visits ending in defeat. Puyol downs Kun about 25 yards out. Chance here...
GLORIOUS CHANCE FOR AGUERO! What has he done?? In the clear, the Argentine had the goalkeeper to beat but bizarrely opted to pass to Simao on the far post and Puyol got back to clear. That was a great chance. Terrible decision from Kun however. Barca can breathe a sigh of relief, he was 15 yards in the clear after a run from halfway.
Pedro upended by Tiago, free to Barca. This is the first time Barca have trailed in the Primera Liga this season and they have work to do now to maintain their healthy lead at teh top of the table.
Messi fires a shot straight at De Gea after cutting inside onto his left but it's simple for the keeper.
Reyes made a superb solo run and played the Uruguayan through the middle and Valdes had no chance as his first time effort nestled in the bottom left hand corner.
Goal Diego Forlán
Substitution Seydou Keita Pedro
Injury Seydou Keita
Maxwell, Puyol and Gaby Milito makes up the rest of the back four for the Blaugrana as Seydou Keita looks to be struggling and may have to come off. Further injury woes for Barca as Pedro is to be introduced at this early stage.
We're underway and Jeffren's first efforts at right back are impressive as he dispossesses Simao.
Kick-off is moments away. Can Atletico Madrid do the unthinkable and help city rivals Real by beating Barcelona. Follow all the action LIVE from the Vicente Calderon LIVE with Goal.com.
Times In BST
Live Final scheduled Suspended Cancelled Postponed