In this series, Jonathan Wilson retells the stories of the five greatest Champions League matches this century. Last week, we revisited Real Madrid's 4-0 demolition of Bayern Munich as Pep Guardiola's coaching philosophy well and truly under the microscope. Now onto number three, when the dying embers of his great Barcelona side took a 3-0 lead, and of course Lionel Messi, to Anfield to face Jurgen Klopp's Liverpool in the 2019 semi-finals second leg. In the bag, surely?
 

3) Liverpool 4-0 Barcelona (semi-final second leg, 2019)
 

Once upon a time three-goal leads were to be respected. Once upon a time they meant something. Once they seemed as good as impregnable. Not any more. Since Barcelona beat Paris Saint-Germain 6-1 in 2017, it seems barely a week of knockout games goes by without another three-goal lead being lost. Barcelona had lost one the previous season in Rome but still, as they went to Anfield in 2019, the prospect of them failing to reach the Champions League final seemed remote.

It wasn’t just that they led by three. It was that they had won the first leg 3-0. When they’d gone out to Roma the previous season it was after having won the home leg 4-1. At Anfield an away goal would make Liverpool’s task all but impossible – and they had Lionel Messi playing some of the best football of his career. He had been the difference in a first leg in which Liverpool had actually played pretty well: how much better would Liverpool have to be, not only to score the three goals needed to take the game into extra time, but also to avoid conceding? And how could they be better without Mohamed Salah and Roberto Firmino, both of whom missed the second leg through injury.

As it turned out, although Liverpool were better in the second leg, the major difference was that Barcelona were worse. With hindsight, their collapse could be seen coming. They’d struggled repeatedly away from home in European competition. There’d been the 4-0 defeat away to Paris Saint-Germain and the 4-1 defeat to Roma. Even in the fortuitous 1-1 draw at Chelsea the previous season, the evidence had been there: because Barca’s forward line pressed only intermittently, its midfield frequently became stretched, exacerbating the basic issue of its lack of pace, making it vulnerable both to teams who pressed it hard, or who were able to counter in such a way as to release runners from deep.

Messi, so influential in the first leg, was cut adrift. Luis Suarez, who had also scored in the first leg, managed just 31 touches in the 90 minutes. This was the final systemic collapse of a once great side, the remnants of Guardiola’s brilliant team of 2008-12, which had been briefly re-energised by the arrival of Suarez and Neymar under Luis Enrique, forced belatedly to confront its decline and the shambolic nature of the attempts in the transfer market to rejuvenate a creaking squad.

And of course Liverpool were excellent, relentless and incisive, enjoying one of those nights when the reputation of Anfield becomes almost self-fulfilling, players feeding off fans, feeding off players feeding off fans, leaving the opposition helpless against the surge. Jurgen Klopp had experienced it in the Europa League in 2016 when three goals in the final 24 minutes overturn a Borussia Dortmund lead, and he inspired it here.

Received wisdom suggests that on such nights the chasing team needs an early goal, or at least to lead by half-time, something to convince them the comeback is possible, and spread doubts in the opponent. Liverpool got their first goal amid their habitual early surge, Divock Origi knocking in the rebound after Jordan Henderson’s initial shot had been saved after seven minutes.

Obviously to speak of ideals in such circumstances is faintly ridiculous: nobody is going to turn goals down. But for Liverpool 1-0 probably was the perfect half-time score because it left Barcelona vulnerable and yet still with a two-goal lead that made them reluctant to over-attack. And they had shown their threat in the first half; it’s easy to forget that Alisson made three good saves in that first half. But when the onslaught came, there was no time for Barca to reset, recover and react.

It was Trent Alexander-Arnold who proved the key, his influence indicative, perhaps, of how Barca’s structure rendered them vulnerable to players coming from deep. The right-back’s low cross was turned in by Georginio Wijnaldum after 54 minutes. Hope was kindled. Two minutes later, it was full aflame as Wijnaldum headed in Xherdan Shaqiri’s cross. Barcelona almost visibly wilted, which perhaps contributed to their doziness as Alexander-Arnold’s quickly taken corner was whipped in by Origi.

The unthinkable had happened and as it did, Klopp confirmed his place as one the great coaches, somebody who had developed the high-octane hard-pressing style that had supplanted possession-heavy juego de posicion as the pre-eminent form of the game. At the same time, it confirmed the end of the great Barcelona, too old to live with such verve, their style outstripped by progress.
 

No 5 – Guardiola's Barcelona humble Man Utd in Rome   
No 4 – Ramos and Ronaldo crush Bayern in Bavaria    
No 3 – Klopp's Liverpool pull off a miracle against Barcelona
No 2 – Mourinho loses but proves his point at the Nou Camp
No 1 – Liverpool edge gloriously chaotic classic in Istanbul