The City manager than stumbled on something which, ultimately, felt like a crucial difference in the quarterfinal tie that ended with a comprehensive 5-1 aggregate victory for Jurgen Klopp's team.

"Liverpool have won this competition five times," Guardiola said. "They believe it is their cup."

Belief is a big word in football, and Liverpool have never lacked self-confidence and conviction in the Champions League -- and European Cup before that -- even when seemingly faced with the impossible.

Their players are often driven on by the club's supporters, especially those with memories of final wins in Rome (twice), London, Paris and Istanbul, and they played their part during this emphatic, two-legged victory over the Premier League's champions-elect.

City's fans, on the other hand, continue to boo the Champions League anthem and give off the impression that they do not feel at home -- or welcome -- among Europe's elite.

This competition fits Liverpool like a glove, and they will go into Friday's draw for the last four not only believing in their prospects of a sixth title on the basis of past successes but also because Klopp's team are gelling into one capable of beating the best to win it.

The elimination of Barcelona, stunned by Roma in Italy, will only improve Liverpool's chances, but the reality is that they have genuine football reasons for believing that Kiev can be another city to deliver European glory.

The obvious strength of the Anfield outfit is the goal threat provided by Mohamed Salah, who scored his 39th goal of the season in all competitions to equalise on the night against City at the Etihad, as well as his fellow forwards Roberto Firmino and Sadio Mane.

It seems that the very best teams attack with a three-pronged strike-force, and Liverpool's triumvirate is as good as any. Given that they have outlasted Barca's Lionel Messi, Luis Suarez and Ousmane Dembele, there will be no inferiority complex, regardless of whom Liverpool face next.

But away from an attacking threat that has been present all season, it is a much-maligned rearguard that is giving Klopp and Liverpool grounds for optimism.

As Georginio Wijnaldum told ESPN FC last month, Liverpool are about more than their front three, with the Dutch international midfielder insisting that equal credit was due to the defenders, who have come under so much criticism this season.

On Tuesday, they conceded inside two minutes when Gabriel Jesus gave City hope, but in the end, it was the only goal Liverpool allowed in 180 minutes against opponents who average almost three goals per game in the league.

"Over two legs, I think we deserved to go through," Klopp said. "We scored five and conceded one, and these numbers are not usually possible against a team like City. City are the best team in the world at the moment, but I knew we could beat them. It doesn't make us a better team, but we are in the semis, so we can enjoy the moment."

Klopp was enjoying the moment, and deservedly so. Denying Guardiola's side a goal in the first leg at Anfield, when the back line and midfield were exceptional, provided the platform for Liverpool's eventual victory in the tie. They have conceded just three goals in their past eight games in all competitions, and Jesus' effort was the first they have shipped in the Champions League since November.

Virgil van Dijk's arrival from Southampton as the world's most expensive defender in January has had the desired effect, with the Dutch international providing leadership and strength at the heart of the back four. Alongside him, Dejan Lovren has rediscovered his form while goalkeeper Loris Karius is beginning to look like the No. 1 Klopp had in mind when he signed him two years ago.

Trent Alexander-Arnold and Andy Robertson are developing into key men at full-back, and in front of them on Tuesday, Wijnaldum proved an able deputy for the suspended captain Jordan Henderson in the defensive midfield role.

Liverpool's front three might get all the headlines, but their success is increasingly down to the solidity that is developing at the back. Klopp's side are not quite as obdurate as that of the Rafael Benitez team that won the Champion League in 2005, but they possess more flair and cutting edge, and it is proving to be a perfect blend.

Their next challenge is to go all the way. Liverpool have won just one trophy this decade -- the 2012 League Cup -- but they now have the chance to win the biggest of them all.

"Barca, Bayern Munich, Real Madrid won everything in the last 20 years. That's pretty much the same time that this club has won virtually nothing," Klopp said. "You cannot become a good team overnight, and we are still developing, but we are here, and we deserved it, and I am really happy about that."

Liverpool are knocking on the door and beginning to believe they can be kings of Europe again.