Jurgen Klopp broke his promise. A few months ago, he had vowed to stop talking about his greatest comeback, his greatest night. There can be a temptation to mention the most famous of his 472 games in charge of Liverpool, in part because it combined so many of the elements that have defined his reign. But after another four-goal comeback, he reached for the ultimate in his search for something reminiscent.

“I promised my team a few months ago that I would never mention the Barcelona game as an example and I used it again today so I broke my promise,” he said. “Just because this game was, before the game, kind of similar.”

It is not often Luton Town find themselves bracketed with Barcelona. It was the shared sense of adversity that prompted Klopp to make the comparison. He likes the idea of limitless possibilities, of making the improbable possible and then actual. Liverpool were underdogs against Barcelona and they definitely were not against Luton, they trailed by three goals to Lionel Messi and co and just one to Carlton Morris and his colleagues, but these were Liverpool sides with a difference, both depleted by injury.

“This team that time ignored the fact who was missing and I want us to ignore the fact who is missing,” Klopp said. Five years ago, Mohamed Salah and Roberto Firmino were the most high-profile absentees. On Wednesday, the 10 who were sidelined included not just Salah but Darwin Nunez, Diogo Jota, Dominik Szoboszlai, Curtis Jones, Trent Alexander-Arnold and Alisson. The opposition were weaker but so were Liverpool.

Yet Virgil van Dijk, Cody Gakpo, Luis Diaz and Harvey Elliott scored. If the role of the left-footer who deputised for Salah on the right was filled wonderfully by Xherdan Shaqiri against Barcelona, now Elliott stood in superbly. Liverpool scored three goals after the break in the second leg of the 2019 Champions League semi-final, four in a match that may or may not help produce a Premier League title. “The second half was a thunderstorm, wow,” said Klopp. “I thought we saw Anfield, saw Liverpool, saw their full-throttle football,” said the beaten Luton manager, Rob Edwards. “Their counter-pressing football was amazing.”

A common denominator came in the ferocity of the onslaught. Once again, it was Liverpool at their most intense, their most irrepressible. But there was also the speed of thought, the goal that stemmed from the coolness possessed by a few people amid a frenzied atmosphere. Rewind five years and perhaps the most celebrated, most remarkable goal of Klopp’s tenure was the fourth, the strike that ultimately eliminated Barcelona: Trent Alexander-Arnold’s quick, low corner, the cult hero Divock Origi’s finish.

It was not a doppelganger but there was a sequel in the strike to put Liverpool ahead, again stemming from a young right-back catching their visitors out. “A genius moment and a quick set-piece,” Klopp said. There was Conor Bradley’s throw-in, Alexis Mac Allister’s first-time cross, Gakpo’s headed finish, all in the blink of an eye. “Cody’s goal, exceptional,” said Klopp. “Quick thinking. Boom, a grenade into the box and he puts his head there.”

There were two goals from a Dutch source against Barcelona, too, with Gini Wijnaldum’s brace then including a header. They are imprinted on Klopp’s mind: five years on and unprompted, he ran through the four goals against Barcelona, highlighting the inspirational leadership of his captain, Jordan Henderson. His successor with the armband, Van Dijk, was the only player to start both games. As their manager noted, this was a result for a new team.

“This is now their Barcelona, it was against Luton,” Klopp said. “Difficult situation, plenty of reasons to give up in moments but not tonight and I saw only a super group fighting. If you don’t limit yourself with bad thoughts you can fly, that’s what the boys did.”

Liverpool took flight under Klopp; the Barcelona game meant they went higher than most envisaged when he took over a team 10th in the Premier League that, within four years, became champions of Europe. Now the pursuit of a quadruple is another attempt to reach stratospheric heights, fuelled by belief. “The conviction to go for it,” Klopp grinned.

Liverpool went for it and perhaps, in the last few months of his reign, Klopp can revive his promise not to talk about Barcelona. He has another comeback to call upon when he wants to motivate his team. “I will mention this game quite a few times from now on,” he said.