Porto 1-4 Liverpool (1-6 agg): Sadio Mane, Mohamed Salah, Roberto Firmino and Virgil van Dijk score

It was in the 65th minute that absolute confirmation arrived. A glorious pass from Trent Alexander-Arnold sliced Porto’s defence in half and Mohamed Salah galloped away to apply a serene finish.

Here was a goal that was so easy on the eye, the sign of a team that is functioning perfectly, but what followed was even more revealing. The celebrations were sober on the pitch, just as they were up in the stands, while Jurgen Klopp’s first reaction was to make a substitution. It was all very subdued.

If you thought this was something to do with complacency, though, you should think again. Liverpool are heading into a semi-final clash with Barcelona – ‘a crazy achievement,’ Klopp said – and they possess the ruthless look of a team that could go all the way.

Liverpool progressed 6-1 on aggregate after winning 4-1 on the night against Porto in their Champions League quarter-final

Virgil van Dijk put the icing on the cake with Liverpool's fourth goal of the evening with a header from six yards out

Virgil van Dijk put the icing on the cake with Liverpool’s fourth goal of the evening with a header from six yards out

The Dutch centre back jumps in the air after getting his name on the scoresheet at Estadio do Dragao on Wednesday

The Dutch centre back jumps in the air after getting his name on the scoresheet at Estadio do Dragao on Wednesday

Roberto Firmino added Liverpool's third goal of the game as they set up a Champions League semi-final clash with Barcelona

Roberto Firmino added Liverpool’s third goal of the game as they set up a Champions League semi-final clash with Barcelona

Firmino plants a low header into the corner of the net to put Liverpool 3-1 up on the night and 5-1 ahead on aggregate

Firmino plants a low header into the corner of the net to put Liverpool 3-1 up on the night and 5-1 ahead on aggregate

MATCH FACTS, PLAYER RATINGS AND MATCH ZONE 

PORTO (4-3-3) Casillas 7; Militao 7, Pepe 7, Felipe 7, Alex Telles 6; Otavio 6, Danilo 6, Herrera 6; Corona 7, Marenga 5.5, Brahimi 6 

Subs not used: Vana (GK), Maxi Pereira, Torres, Costa, Andre Pereira, Soares, Fernando

Goals – Militao 68

Booked – Pepe

Manager – Sergio Conceicao 7

LIVERPOOL (4-3-3) Alisson 7.5; Alexander-Arnold 6.5, Matip 8, Van Dijk 7, Robertson 7; Milner 6.5, Fabinho 6, Wijnaldum 6; Salah 7, Origi 6 (Firmino 46mins), Mane 7.5 

Subs not used: Mignolet (GK), Keita, Firmino, Gomez, Henderson, Sturridge, Shaqiri

Goals – Mane 26, Salah 65. Firmino 77, Van Dijk 84

Booked – Mane

Manager – Jurgen Klopp 7–

Referee – Danny Makkelie (Netherlands) 7

Man-of-the-Match – Joel Matip

This is how Mohamed Salah scored Liverpool’s second goal of the evening to put them 4-0 ahead on aggregate at Estadio do Dragao. CLICK HERE to see our brilliant MATCH ZONE.

For all the talk about Liverpool winning the Premier League, Europe may yet provide the silver sheen to this outstanding season. This was a difficult night in Northern Portugal but they got through it with a combination of indefatigable defending and clinical finishing.

They are a better a team than the one that won 5-0 at this venue last February and they are better than the team that reached the Champions League final last May. True, Lionel Messi will provide an a totally different test but who is to say Liverpool won’t go all the way?

Sergio Conceicao, Porto’s manager, described Liverpool as ‘the best team in the world’ in the build up to this clash. Plenty will argue about the merits of that statement but what can be said with certainty is the fact they have the best defence in Europe.

The hour before kick-off saw a downpour so heavy that you wondered whether it would force the match officials to delay kick-off; the rain fell so hard, though, that it was clearly going to affect the playing surface and you could see how much in the opening moments.

Eder Gabriel Militao pulled a goal back for Porto to make it 2-1 on the night against the Premier League giants

Eder Gabriel Militao pulled a goal back for Porto to make it 2-1 on the night against the Premier League giants

The Porto man celebrates after grabbing a consolation goal for the Portuguese outfit on Wednesday night

The Porto man celebrates after grabbing a consolation goal for the Portuguese outfit on Wednesday night

Mohamed Salah scored Liverpool's second goal of the night, slotting home past Iker Casillas from close range

Mohamed Salah scored Liverpool’s second goal of the night, slotting home past Iker Casillas from close range

The Egyptian star wheels off to celebrate after scoring the Reds' second goal of the game at the Estadio do Dragao

The Egyptian star wheels off to celebrate after scoring the Reds’ second goal of the game at the Estadio do Dragao

Salah celebrates his goal with Trent Alexander-Arnold, who provided the goal for the in-form, speedy winger

Salah celebrates his goal with Trent Alexander-Arnold, who provided the goal for the in-form, speedy winger

‘It was tough, that’s what we expected,’ said captain Jordan Henderson. ‘They make it intense but we kept going. You could see the effort that we put in.’

Liverpool wanted to take the sting out of the contest by keeping possession at the back but it was a decidedly dangerous tactic, as each pass between Virgil van Dijk, Alexander-Arnold and Alisson Becker would check on the spongy surface. There was no zip and it invited Porto to come forward.

It was not as if the hosts needed any encouragement. The noise inside this cavernous arena was wonderful, with ear-splitting whistles aimed at Liverpool and the match officials and bellowing screams of encouragement for those in blue-and-white.

Bookmakers had Liverpool as 1/50 to progress but those odds were an insult to the Portuguese, who had their first shot after 37 seconds when Jesus Corona skipped inside Andrew Robertson and crashed a drive just over the bar.

This was a sign of things to come. Too many players had started slowly and the contest could easily have had a different complexion had Moussa Marega not been so profligate; the Malian had been wasteful in the first meeting at Anfield and the same was true here.

Sadio Mane killed the tie after tapping home in the 26th minute to give Liverpool a 3-0 lead on aggregate

Sadio Mane killed the tie after tapping home in the 26th minute to give Liverpool a 3-0 lead on aggregate

Mane taps home from close range as Porto goalkeeper Iker Casillas desperately attempts to close him down

Mane taps home from close range as Porto goalkeeper Iker Casillas desperately attempts to close him down

Mane checks to see if the offside flag has gone up as Casillas protests to the linesman on the far side on Wednesday night

Mane checks to see if the offside flag has gone up as Casillas protests to the linesman on the far side on Wednesday night

Salah plays the ball across to Senegal international Mane as Liverpool put the result of the tie beyond doubt

Salah plays the ball across to Senegal international Mane as Liverpool put the result of the tie beyond doubt

The goal was initially ruled out for offside but referee Danny Makkelie looked at VAR before awarding Liverpool's strike

The goal was initially ruled out for offside but referee Danny Makkelie looked at VAR before awarding Liverpool’s strike 

Mane is mobbed by his Liverpool team-mates after scoring the opening goal during the second-leg against Porto

Mane is mobbed by his Liverpool team-mates after scoring the opening goal during the second-leg against Porto

Twice in the space of 60 seconds Marega had the opportunity to bring this cauldron to the boil but he planted one header wide from 10 yards after sneaking in between Joel Matip and van Dijk then, in the next attack, he scuffed a volley from an Alex Telles cross the wrong side of the post.

There was anguish in the roar that accompanied the latter miss. Porto had to connect with one of these big swing, as sooner or later Liverpool were going to get an opening of their own. When it arrived in the 28th minute, any lingering doubt about the contest was removed.

For once Liverpool managed to put a sequence of passes together; Andrew Robertson and Mane exchanged played a one-two, Gini Wijnaldum helped it along to Salah and the Egyptian’s attempted shot squirted to the back post where Mane slid in to apply the finish.

Inevitably, there was fury amongst the home supporters but the longer the match officials spent deliberating, there was an inevitability about the outcome. Salah, who had been watching the replays on the pitch side monitor, started celebrating 10 seconds before the signal was given.

Divock Origi wrestles for the ball with Porto defender Felipe at the Estadio do Dragao during the closing stages of the game

Divock Origi wrestles for the ball with Porto defender Felipe at the Estadio do Dragao during the closing stages of the game

Former Real Madrid defender Pepe appears dejected during the crunch European clash against Jurgen Klopp's men

Former Real Madrid defender Pepe appears dejected during the crunch European clash against Jurgen Klopp’s men

Porto manager Sergio Conceicao quickly gives the ball back to Militao with his side chasing three goals

Porto manager Sergio Conceicao quickly gives the ball back to Militao with his side chasing three goals

Alisson makes a smart save as the Portuguese giants get off to a strong start in their bid to overcome a two-goal deficit

Alisson makes a smart save as the Portuguese giants get off to a strong start in their bid to overcome a two-goal deficit

A look at footage showed the decision to be correct – Felipe, the Brazilian left-back, played Mane onside – and, amid the commotion, it was also impossible not to overlook just how important the Senegalese flyer has become.

He has now scored the first goal for Liverpool eight times in the last 14 matches and his quality and consistency has been such that it will be a surprise if he does not make the six-man shortlist for Player of the Year. This is a man with a special talent at the top of his game.

One was always going to be enough but Liverpool went through the gears in the second half; Salah’s strike was glorious, Roberto Firmino added the third from Henderson’s cross and van Dijk rubbed salt in the wounds late on with a header to render Eder Militao’s strike nothing other than a footnote.

Klopp, undoubtedly, will pick faults in what he saw but, generally, Liverpool are in outstanding shape. They have now won their last eight matches in all competitions. Carry on in this manner and they might win the trophy that was once part of this club’s furniture.

Georginio Wijnaldum battles for the ball in the air with Otavio as both sides look to get off to the perfect start in Porto

Georginio Wijnaldum battles for the ball in the air with Otavio as both sides look to get off to the perfect start in Porto

Salah fights for the ball with Porto's Alex Telles during the opening stages of the clash in Portugal on Wednesday

Salah fights for the ball with Porto’s Alex Telles during the opening stages of the clash in Portugal on Wednesday

Porto supporters made a raucous atmosphere before kick-off in the second-leg as they held up banners of their players' faces

Porto supporters made a raucous atmosphere before kick-off in the second-leg as they held up banners of their players’ faces

Jurgen Klopp waits for the action to get underway ahead of the second-leg at the Estadio do Dragao on Wednesday

Jurgen Klopp waits for the action to get underway ahead of the second-leg at the Estadio do Dragao on Wednesday

Read more at DailyMail.co.uk