Having come on at half-time for the injured Diogo Jota, Firmino’s superbly guided header from Andy Robertson’s corner earned the Merseysiders a 75th-minute lead at the home of the Italian champions.
Salah then doubled that advantage in the 83rd when he raced onto a Virgil van Dijk knockdown in the box and fired home a deflected left-footed effort.
A second win of the season at the wonderfully atmospheric San Siro, after the 2-1 group stage victory over AC Milan in December, and a firm foundation to take into that return leg in a little under three weeks.
Prior to the two goals – which were the only shots on-target of the evening – there had been relatively little between the sides.
Sadio Mané had sent a free header from a 14th-minute Robertson free-kick over, while Hakan Çalhanoğlu struck the underside of the crossbar for the hosts two minutes later after he took Ivan Perišić’s cross nicely in his stride and shot left-footed.
Inter looked to be in the ascendency early in the second period. Another Perišić delivery just evaded Lautaro Martínez in the 53rd minute while I Nerazzurri’s press was offering the visitors increasingly little room for manoeuvre.
Few genuine openings materialised, though, and a 59th-minute triple substitution – which saw Harvey Elliott, who became the youngest player to start for Liverpool in the Champions League, Fabinho and Mané make way for Naby Keïta, Jordan Henderson and January signing Luis Díaz – helped to reset the game’s trajectory in the Reds’ favour.
The goals followed, as Klopp’s side retained and enhanced their solidity while offering additional cutting edge.
Reds’ depth offers bench boost
That triumvirate of changes just prior to the hour mark proved a significant bookmark in the match and reflected the promising current context of the Merseysiders’ squad.
Each of Keïta, Henderson and Díaz – the latter of whom scored at the San Siro for Porto earlier this season – offered a combination of additional energy, pace and physical and technical intensity upon their introduction.
The availability of five substitutions in the Champions League enabled the Liverpool coaching staff to utilise the range of traits within a squad that looks particularly rounded and deep, at present.
Prior to Jota’s ankle knock in the first half – which the club will reportedly assess on Thursday – there appeared to be a clean bill of health within the Reds’ ranks.
The hope will be that the Portuguese forward’s issue isn’t too serious, of course, but Liverpool’s ability to adapt their approach on Wednesday was certainly good to see.
Having not scored a goal from a non-penalty set-piece in the 11 games between Van Dijk converting a Trent Alexander-Arnold corner against Southampton on 27th November and Fabinho doing likewise against Brentford on 16th January, Liverpool have now scored six from set-plays in their last seven games.
The latest effort in that regard, courtesy of Robertson and Firmino, had a superb precision to it, with the Brazilian flicking the Scot’s near-post delivery into what felt like the tightest of gaps between the reach of Samir Handanovič and the far-post.
That additional productivity from set-pieces has proved highly valuable in recent weeks and, if the threat can be sustained over the coming months, it has the potential to prove a decisive factor in several matches – and over the course of the season.
It’s an attribute that adds further to the roundedness of the Reds’ approach.
That’s a phrase that could be applied to Wednesday night in several senses for Liverpool. Again, it could well also be an important, widely applicable one, moving forwards.
The centre-back partnership of Ibrahima Konaté and Van Dijk is one such application.
They were consistently strong, swift, focused and assured against Inter. Particularly when having to defend in greater portions of space, which did occur courtesy of turnovers or counter-attacks.
That is, indeed, an element of the game they are regularly trusted with given the measured risks that generally appear to be present within the team’s setup.
Each of Konaté, Van Dijk and Joël Matip have largely been excellent in their reading and contributions to the game with and without the ball this term – especially, it feels, in recent weeks.
Alisson Becker and Fabinho are two more who contribute sizeably to that defensive foundation, of course.
While the goalkeeper may not have – in the end – had a genuine save to make at the San Siro, he remained a confident, commanding presence throughout.
Fabinho was also positively aggressive and dominant in midfield at times, especially in spells within the first half.
Henderson then offered his own attributes within that role.
The former Sunderland man’s ability to move the ball swiftly and to set and maintain tempo again came to the fore here – particularly given it followed a period where the hosts had earned a reasonable foothold.
Once more, the variety and reliability of those central defensive structures within the team offer Klopp’s side another solid foundation from which to build.
A notable factor in allowing them to earn a solid base in this tie ahead of 8th March.