At the time, nobody was aware quite how defining a moment it would be.
But, like all the greatest footballers, Lionel Messi knew the potential significance. He knew it all too well.
Having raced away during injury time at Camp Nou in the first leg of the Champions League semi-final in 2019, Messi laid it on a plate for Barcelona substitute Ousmane Dembele to score a fourth and surely put Liverpool to bed.
FLASHBACK: Fabinho takes Lionel Messi to school as Kop has last laugh at Luis Suarez
Thankfully for the Reds, Dembele finished horribly, the chance gone. A 3-0 defeat was bad enough, but 4-0 would have been insurmountable.
No wonder Messi beat the turf in frustration at the failure of his team-mate.
“It was very clear, it would have been better to finish with four than with three,” said the Argentina international after that first leg. “We know the game isn't over, we know we're going to a very difficult stadium with a lot of history, where the fans are really behind their team."
Messi knew. He knew it all too well.
So when Divock Origi struck the fourth goal to send Anfield into delirium exactly four years ago today, the World Cup winner could be spotted with his hands on his hips, wondering why on earth his team-mates had wilted in such remarkable fashion.
Barcelona were well beaten by then, a spent force unable to muster much of a response to going behind on aggregate.
Messi, to his credit, kept on plugging away. But with Liverpool, primed by Fabinho, locking him down, the Argentine was, to a large extent, neutered.
Luis Suarez knew precisely what to expect - describing the fans as Liverpool's "12th man" in the build-up - but even he was powerless to repel the power of Anfield. Philippe Coutinho, for whatever reason, didn't even bother an attempt.
Messi was only 19 on his previous appearance at Anfield, on the winning Barcelona side on the night but beaten on aggregate in the Champions League first knockout round in 2007. This time, though, he was spotted as the teams lined up for the Champions League anthem, taking a glance at the swaying, baying Kop.
But it wasn't just the crowd that Messi feared would make an impact.
After the first leg, he admitted to the Spanish press he was "exhausted" by coming up against a relentless Liverpool side, whose superior fitness and energy levels told during the final quarter at Anfield.
Messi knew Liverpool - even without injured duo Mohamed Salah and Roberto Firmino - would not give up.
George Sephton, the voice of Anfield, played out the evening with John Lennon's Imagine. Liverpool, over the course of the 90 minutes, turned from doubters into believers.
And while Barcelona's mystique was shattered, the glory of Madrid, Istanbul and Doha was still to come for Jurgen Klopp and his players, along with a first championship in 30 years and the FA Cup and League Cup. The clean sweep was beginning.
As is once again being shown during the closing weeks of this difficult campaign, no matter what the situation, Liverpool under Klopp won't give up without an almighty fight.
A version of this story first appeared on May 7 2020
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