Jürgen Klopp gave a passable impression of a Uefa PR executive in billing the reunion with Porto as tough for Liverpool. True, there was no slaying of the Dragons by his team this year. No real danger for them either. The Premier League leaders are on course for the Champions League semi-finals after controlling this first-leg tie with the experience and guile of seasoned campaigners.

It was not always serene for Klopp’s team at Anfield. Had visiting forward Moussa Marega converted one of several presentable chances for an away goal or Mohamed Salah been punished for a bad challenge on Danilo, the complexion of next Wednesday’s second leg would have been very different. Marega did not, Salah was not, and it underlined the comfort level Liverpool enjoyed that Klopp could substitute Sadio Mané and Roberto Firmino in readiness for Sunday’s vital meeting with Chelsea. A far from taxing European victory and no injuries. Perfect, in other words, for a team chasing their dream of the Premier League title.

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Firmino was on the scoresheet in a deserved win that, with better decision making and precision in the second half, could have been a comprehensive one. Naby Keïta was also off the mark in Europe for Liverpool as he delivered an incisive performance in central midfield, where Jordan Henderson dominated throughout.

The Porto coach, Sérgio Conceição, claimed “negative thoughts are in the past” when dismissing the impact of Liverpool’s 5-0 defeat of his team last February. Klopp was equally unconvincing in his assertion that the two-times European champions were the last team he wanted to face in the last eight. With a defining, demanding period in the title race to come for Liverpool and Manchester City, the Portuguese side were the best remaining option available. So it proved.

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As in the first leg of the last-16 tie last season Porto opened confidently and sharply, with Conceição showing no thought of containment away from home in his deployment of a three-pronged attack and a high defensive line. And, once again, his team were two goals down and looking ripe for a hiding before the half-hour mark.

Liverpool commenced their routine win earlier this time, puncturing Porto’s optimism and tame resistance with their first attack. James Milner, deputising for the suspended Andy Robertson at left-back, swept a raking pass out to Mané on the left. The Senegal striker found Firmino inside the penalty area, he teed up Keïta and the midfielder’s shot sailed into the top corner via a kind deflection off Óliver Torres. Iker Casillas had no chance but every right to question the marking in front of him. For Keïta, it was a second goal in two games for Liverpool having gone 27 appearances without one. Another Klopp selection had been vindicated in quickfire fashion.

Facebook Twitter Pinterest Naby Keïta celebrates the first goal with Liverpool’s other goalscorer, Roberto Firmino. Photograph: Carl Recine/Action Images via Reuters

The hosts created several chances to double their advantage before Firmino put them further ahead. Porto’s shape and composure disappeared in the immediate aftermath of Keïta’s opener. Jesús Corona was unsure of the help he was supposed to offer Maxi Pereira at right-back while Salah tormented Alex Telles on the left. Henderson applied the cuts and the thrusts almost unchallenged. Firmino had a shot deflected wide. Salah, who brought Anfield to its feet by chasing back to dispossess Otávio inside his own area, had a glorious opportunity when the Porto forward pierced his central defence with a ridiculous pass. It would have been a great one had it been sent in the right direction, mind. Salah pounced, rode what could easily have been a foul by the last man, Felipe, and rolled a shot beyond Casillas but also the far post.

Porto were not reprieved for long. Firmino started and finished the second when he picked out Henderson unmarked in central midfield. The captain threaded a superbly weighted pass behind Telles into the run of Trent Alexander-Arnold, and his first time cross was tapped home by the Brazil international.

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Liverpool were coasting as expected yet Marega should have injected doubt when he had two clear sights of goal in as many minutes. The powerful Porto striker, who came into the game with six Champions League goals this season but had been ill in the hours before kick-off, found himself one-on-one with Alisson when a clearance deflected into his path. Marega had to score to give his side hope. The legs of the Liverpool goalkeeper ensured he did not. The attack stayed alive and VAR was called on to assess a handball by Alexander-Arnold after Alisson clawed the ball on to his full-back. Porto were awarded only a corner, VAR spotting the incident occurred off the pitch, and Marega was given a second bite when the ball dropped at his feet on the penalty spot. His shot on the turn was straight at Alisson, to his obvious and understandable despair.

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Henderson thought he had a second assist, and Liverpool a third goal, when he floated an inch-perfect cross over the visiting defence for Mané to volley precisely under Casillas, who was making his 176th Champions League appearance at the age of 37. The assistant referee spotted a fractional offside, however, and VAR backed him up to the audible disappointment of the Kop.

It was to Porto’s credit that they refused to wilt under Liverpool pressure and the sense of deja vu the two first-half goals must have triggered. They rarely threatened to spoil the hosts’ crucial clean sheet, however, and were angered when Salah escaped a card of any colour for going over the top on Danilo in the closing stages. They could have no complaints about their own punishment.