In truth Liverpool secured their place in the Champions League quarter-finals three weeks ago but the formality of victory over Porto does not lessen their achievement. Jürgen Klopp’s team enjoyed the fruits of a ruthless demolition in Portugal and eased into the last eight. “It was time we showed up again,” purred a contented Liverpool manager.

Anfield staged an unusual last-16 second leg: one lacking goals, excitement and the competitive edge the game requires at any level. Liverpool had no complaints. The onus was on the Portuguese league leaders to address their 5-0 first-leg humbling and, courtesy of a professional job by Klopp’s team, they never looked likely to become the first side to overturn a five-goal deficit in the Champions League.

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The return leg was enlivened only after Mohamed Salah’s late introduction but, aside from a spectacular save from his fellow substitute Danny Ings, the veteran keeper Iker Casillas was barely troubled. Liverpool will be hanging around for some time yet on current form. This was more a test of their mentality than ability according to Klopp and it was one they passed with ease en route to their first quarter-final appearance since defeat by Chelsea nine years ago.

“It feels really good, to be honest,” said Klopp. “I cannot feel what people feel about waiting so long but I know about it. The last eight is cool. I am a little bit satisfied. It was time we showed up again. There is good development at Liverpool at the moment but, if you don’t show up in a competition like the Champions League, then nobody will realise it. It’s done, it’s good – now let’s carry on.”

The strength of Liverpool’s squad enabled Klopp to avoid too many risks with his line-up while still making five changes to the team that beat Newcastle on Saturday. Virgil van Dijk and the 32-goal Salah were left on the bench and Andrew Robertson was absent completely but it was an experienced and recognisable Liverpool side that the manager deployed. At a crucial stage in the campaign maintaining their formidable rhythm was also on Klopp’s agenda.

Porto were more disciplined and united than at Estádio do Dragão and almost capitalised twice with long balls over Liverpool’s central defence. The fit-again Vincent Aboubakar and then Majeed Waris just failed to connect. Professional pride was at stake for the visitors, roared on by an impressive travelling support. Impressive in numbers, at least – the failure of a few individuals in the Porto section to honour a minute’s silence for Davide Astori, the late Fiorentina captain, brought understandable condemnation from the home crowd.

The commitment of both teams to victory was undeniable but so was the sense of a dead rubber. The first half was painfully short on incident, although twice Sadio Mané almost inflated Liverpool’s aggregate lead.

His first chance arrived from a right-wing cross by Joe Gomez but an acrobatic volley sailed just over Casillas’ crossbar. His second, a snap-shot from the right of the penalty area, beat the World Cup winner only to rebound to safety off the inside of the far post.

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Casillas was given a warm ovation by the Kop when he re-emerged for the second half of what could be his final appearance on the Champions League stage. His first came in September 1999 when the former Liverpool striker John Toshack named an 18-year-old Casillas in his side to face Olympiakos in Athens – a statistic to make one feel old.

But it was the Liverpool keeper, Loris Karius, who made the first save of the night when Waris shot low to his right. That was a rare moment of danger for Liverpool and they continued to create the better of the game’s few opportunities. James Milner, part of a midfield trio that allowed Liverpool to dominate possession and retain composure throughout, sliced wide when stretching for Adam Lallana’s cross. Lallana made only his third start of an injury-hit season on the left of the attack but was more prominent when switched to his preferred position on the right.

Roberto Firmino, Ings and Salah – who was promised a day off training on Wednesday by Klopp providing he “ran a lot” for the final 16 minutes – all tested the Porto defence in the second half. The goalless draw could not dampen the Liverpool manager’s enthusiasm for his team’s progress.

“I don’t want to make it smaller than it is and I don’t want to make it bigger,” said Klopp. “We belong there, it should not be a big surprise and the next round will be very difficult. We have a chance to go through to the semis, that is the aim, but we take it step by step. It’s cool.”