Liverpool’s task seemed unthinkable: pierce the Barcelona defense four times, keep the ball out of its own net and do it all without one of the world’s preeminent goal scorers, Mohamed Salah.

And then it happened. The Reds played 90 minutes of unimaginably polished soccer in front of a frenzied home crowd. They shut out Barcelona and Lionel Messi, 4-0, winning the Champions League semifinal matchup, 4-3 on aggregate. Their offense was intense. Their defense was laudable. And now they will play for a European title against either Tottenham or Ajax.

Barcelona led, 3-0, after the first leg at Camp Nou, with Messi scoring twice, including once on a majestic, bending free kick. On Tuesday, he made a few dangerous runs through swarms of defenders, but was not able to lift his side this time.

By contrast, Liverpool’s inspired effort had Manager Jurgen Klopp struggling to stick to the usual coach-speak script.

“Most of the children are probably in bed, but these boys are f------ giants," he said on camera, taking note of the late hour. "It’s unbelievable. If you have to fine me, fine me.”

Divock Origi scored on a rebound in the seventh minute, giving Liverpool the start it desperately needed, but Barcelona could still feel fairly confident in its chances. Then the Reds’ Georginio Wijnaldum scored twice — two minutes apart, in the 54th and 56th minutes — before Origi scored again on a sneaky corner kick from Trent Alexander-Arnold in the 79th minute.

Alexander-Arnold went to take the corner, then walked away from the ball. As he did, Barcelona’s defense relaxed, and Alexander-Arnold quickly went back over the ball and swept a low, hard cross to Origi, who slotted it in and gave Liverpool a winning margin that few expected at the start of the day.

“Unbelievable. I don’t think many people gave us a chance,” Liverpool captain Jordan Henderson said. “Before the game we knew that it would be difficult, but it was still possible, of course. It’s amazing. We knew that at Anfield we could do something special.”

For the second straight year, Barcelona found itself on the wrong end of one of a comeback. In 2018, the Spanish colossus squandered a 4-1, first-leg lead against AS Roma and was ousted in the quarterfinals. Manager Ernesto Valverde had said Monday of that humiliation, “We’ve learned our lesson.”

Valverde also described the absences of Salah and another Liverpool standout, Roberto Firmino, as "a big miss for them,” but on Tuesday it was his star-studded side that appeared in need of a boost.

Messi created several promising offensive beginnings, but none of his teammates were finishers. Barcelona keeper Marc-André ter Stegen got his body on one shot, but couldn’t keep it out, and was caught napping on the fourth and decisive goal.

When the clock struck the 95th minute of stoppage time, Anfield Stadium burst into rapturous cheers.

Liverpool became just the third team in the history of the European Cup to advance in the semifinals after falling behind by three goals in the first leg, according to the Associated Press. The others were Panathinaikos, in 1970-71, and as fate would have it, Barcelona in 1985-86.

“Playing against the best team in the world," Klopp said. “Winning with a clean sheet, I don’t know how the boys did it.”

The identity of the Reds’ opponent in the final will be determined Wednesday when Ajax and Tottenham play the second leg of their semifinal showdown. Ajax holds a 1-0 lead on aggregate. For now, Liverpool will savor a mammoth win made all the more unlikely by the quality of its foe.

“I saw [Liverpool veteran] James Milner crying after the game on the pitch. It means so much to all of us," Klopp said. "There are more important things in the world, but creating this emotional atmosphere together is so special.”

Liverpool shocks the world (and Twitter)

Game updates

Liverpool scores again! They lead, 4-0, and 4-3 in aggregate

The Reds are in the midst of a stunner and scored their fourth unanswered goal in the 79th minute off a sneaky corner kick.

Trent Alexander-Arnold stood over the ball at the right corner and caught the Barcelona defense napping. Divock Origi stood in the middle of the box and somehow — without the defense noticing — Alexander-Arnold whipped a pass and Origi tapped it in.

And again! Liverpool goes up, 3-0, ties aggregate score, 3-3

Xherdan Shaqiri’s cross two minutes after Georginio Wijnaldum’s first goal found Wijnaldum again. His header into the top left corner of the goal and gave Barcelona keeper Marc-André ter Stegen no chance.

Liverpool strikes again, leads 2-0

There’s the offense Liverpool has been pressing for. In the 54th minute, Trent Alexander-Arnold pushed up from his right back position to preserve the Reds’ possession and whacked a low cross into the 18-yard box. Georginio Wijnaldum, who subbed in at the half, ran on to it and his shot clipped Barcelona keeper Marc-André ter Stegen’s torso, but not enough to keep it out of the net.

Liverpool leads, 1-0, at the half, but still trails in aggregate

It’s one goal down, three to go for Liverpool, if it wants to advance to the Champions League final. The Reds still trail, 3-1, in aggregate scoring.

Scoring chances are mounting for Lionel Messi and Barcelona, though, as Liverpool has to keep forcing numbers forward to create offense. They still need a bunch of it.

Liverpool scores early

Liverpool got the start it wanted, opening the second leg of its Champions League semifinal against Barcelona with frantic play that led to an early goal. In the 7th minute, Sadio Mane flicked a ball ahead to Jordan Henderson, who wove through defenders and into the 18-yard box, then blasted a shot on goal that was saved, but right into the feet of forward Divock Origi. He didn’t miss his attempt.

Pregame thoughts

Liverpool is technically still alive in the Champions League semifinals. Barcelona’s 3-0 whomping in the first leg came at home in Spain, so Liverpool’s task Tuesday to advance: score four times in the second leg, and keep Barcelona off the board. And they’ll have to do it without star striker Mohamed Salah and midfielder Roberto Firmino, both injured. In other words, good luck.

Liverpool Manager Jurgen Klopp said after the first leg, “I don’t know if we can play much better.” His side led in possession, took more shots, took more corners, and yet only survived the first 70 minutes against a relentless Barcelona squad. Lionel Messi and Luis Suarez wore down Liverpool’s back four. Midfielders Ivan Rakitic and Sergio Busquets kept possession when it mattered. Barcelona went 90 minutes without a mistake and played the last 20 with unmatched brilliance.

Klopp said he expects Salah to be available Sunday for Liverpool’s Premier League finale against Wolverhampton Wanderers. Liverpool is aiming to win its first Premier League title since 1990.

Time: 3 p.m. Eastern.

TV: TNT and Univision.

How to stream online or an app: B/R Live, Watch TNT app, Univision Deportes app.

Location: Anfield Stadium, Liverpool, England.

Barcelona

  • Lead, 3-0, after first leg.
  • Champion of La Liga, winner of Supercopa de España.
  • Last Champions League title: 2015, over Juventus.

Liverpool

  • Trail, 3-0, after first leg.
  • Second place in Premier League (season ongoing).
  • Last Champions League title: 2005, over Milan.

Players to watch

For Barcelona, there is a clear choice: Messi. Messi, Messi, Messi, Messi. His 48 goals this season have world footballing greats insisting he is in a class of his own atop the sport, better than Cristiano Ronaldo. If he doesn’t score during this second leg, he’ll surely create a scoring chance. He’s also virtually unmatched in his performance against English teams in Champions League.

Winger Sadio Mane is Liverpool’s top scoring threat with Salah out of the lineup. He’ll need to have success running behind Barcelona’s well-tested back four and taking defenders on one-on-one. A strong effort that lifts the Reds through to the Champions League final — or even close — could make Mane an overnight folk hero.

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