Danny Makkelie stood there in the middle of the storm, rain pouring down around him, and put his finger in his ear. It wasn’t easy hearing the words coming down the wire, and still less the moment they saw him.

The game was just 28 minutes in, but this already felt like Next Goal Wins and while it seemed certain Porto would get it, it was Liverpool that did. Only they didn’t. Only they did again. Mo Salah provided it, Sadio Mané took it, and the linesman’s flag took it away again. Then the Dutch referee gave it back. As soon as the Porto fans filling the Dragon’s den saw him do that gesture, they feared he might.

Sadio Mané sets up Liverpool for comfortable passage past Porto Read more

Porto had wanted to take the free-kick swiftly and get rolling again, not allowing the momentum they had built to slow, but Makkelie stopped them. Mane had appeared clearly offside, and no one really challenged it. Only Salah, thumbs up, seemed aware the goal might count. But upstairs they were having a look: a routine check now, repeated at every game and after every goal, something new for football to get used to, justice served at the cost of spontaneity. There are reservations about VAR, and this is one of them: the time taken, the emotion too.

Among the Liverpool fans the celebration had died quickly, resigned to losing the opening goal. But the referee put everything on hold, as if there was a pause button in his ear. Porto’s fans whistled; they whistled because they didn’t want to stop and because they knew what this might mean. And so, inside the stadium, they waited. Eventually, the referee drew a screen and pointed to the centre circle. Liverpool’s fans celebrated and, although it was not the same on delay, the wildness gone, they had the lead. They were as good as through. The home supporters fell momentarily silent, stunned.

Quick guide Champions League semi-final fixtures Show Hide Tuesday 30 April: Tottenham v Ajax Wednesday 1 May: Barcelona v Liverpool Tuesday 7 May: Liverpool v Barcelona Wednesday 8 May: Ajax v Tottenham Champions League final to be played in Madrid on Saturday 1 June

Soon they sang again, and loudly, but it was different then, more homage than hope. Mo Salah’s second confirmed Liverpool’s passage and the roar that greeted Éder Militão’s header soon after was about recognition, pride. Roberto Firmino and Virgil van Dijk made it 4-1, 5-1 on aggregate, making this appear more routine than it had originally been while also underlining just how strong, how resilient and how varied this Liverpool team is. How difficult it will be to eliminate them, too.

Mané had done it again – this was his fourteenth goal in seventeen games. And, yet again, it had been the first. The opener and effectively the winner too, silly though that may sound when four more goals followed. It was over and Porto could barely believe it.

Play Video 0:56 Jürgen Klopp 'really happy' Liverpool will play Barcelona in semi-finals – video

Jesús Corona, Moussa Marega, Danilo, Pepe, Éder Militão, Héctor Herrera, Yacine Brahimi, Alex Telles. That’s not the Porto lineup; it is the list of players who’d had chances before Liverpool had scored, the shot count starting after just 33 seconds and rising fast, the noise rising with it. Marega alone had four, a player who did everything well except shoot. When Salah found Mané, the stats for shots read 13-1. The scoreboard said 0-1. By the end, it said 4-1. Ultimately, it had been comprehensive. Liverpool have something, that’s for sure.

Something that suggests that they could win this. After all, there they were, still standing. And standing on the verge of the semi-final of the European Cup. It may be worth saying that again. The semi-final. Of. The. European. Cup.

There is something about Liverpool that makes them different to every other team in the competition this year. Even here, some of the attention appeared drawn to the league. On the face of it, there is something vaguely absurd about the implication that Cardiff City are more important than Porto, that this game could cause collateral damage. But that perhaps says something about Liverpool’s search to finally win the league, 29 years later, an entire generation yet to see them lift the title that once seemed to be theirs.

Jürgen Klopp looks forward to ‘proper game’ with Barcelona in semi-finals Read more

Which is why in the bars of Porto, the debate was no such thing: no one in red doubted that, given the choice, they would take league over the Champions League. Maybe only for this year, maybe only to end the wait, to draw level with United, but they would. It is why at the full-time whistle, some in the stadium even dared suggest that this had been a bad night: those extraordinary scenes in Manchester meant that City would not relinquish the league now, they reasoned.

They may even be right. Yet it was as if this was not so big, after all, when it is it is huge. Maybe that domestic obsession has hidden something that, for any other club, would be everything: Liverpool could win their sixth continental title. If they do make it to the Metropolitano, it would be their fourth final in fourteen years. And in that time no one has appeared in more. Last night, under cover of the league, Jurgen Klopp’s slipped into the semi-final of the European Cup.