Though Liverpool's forwards grab the headlines -- even Sadio Mane scored a hat trick at Porto last Wednesday -- another player is delighting the fans for different reasons.
Left-back was always a thorny position for the Reds. There have been poor players, like Andrea Dossena and Paul Konchesky; there have been unlucky players, like Fabio Aurelio and Jim Beglin. Even the most consistent of them, John Arne Riise, could infuriate at times with rare consensus over whether he was really a defender or a midfielder.
When Andrew Robertson signed from Hull in July 2017 there was little fanfare, just an expressed hope he couldn't be any worse than Alberto Moreno.
Having used James Milner out of position for all of the 2016-17 season, signing Robertson was an admission from Jurgen Klopp that a proper left-back was required.
Confusion then reigned when Klopp generally persisted with Moreno, which saw Robertson's chances to shine sporadic. In fairness Moreno vaguely improved his game, and though Liverpool still leaked goals, little blame was attached to Moreno for them (one dreadful performance at Sevilla aside.)
Fortune often comes to a manager's rescue and injury meant Klopp had no choice but to take a chance on Robertson. And in the main he's been exceptional from the moment Moreno limped off the pitch against Spartak Moscow on Dec. 6.
The stellar performances of Mohamed Salah and Roberto Firmino kept the goals flying in for Liverpool. Decent results also kept the spotlight off Robertson, ensuring he could get games under his belt and become a fixture in the team.
It's a big part of any manager's job to make sure younger players don't get carried away and let fame go to their head. Having played well over 100 games for Hull City already, that doesn't appear to be a problem for Robertson, but it's early days yet.
Younger players than Robertson tried to fix this problem position with early success, only to fade for different reasons. Jon Flanagan and Emiliano Insua looked good in title-challenging sides, yet when the team began struggling they did, too -- although Flanagan was continually hampered by injury.
The woes of Moreno have been well documented, with comparisons to Riise over whether he'd make a better left-sided midfielder than a defender.
Robertson has his gung-ho moments, too, but it's telling that he instinctively races back into position whenever a Liverpool attack breaks down.
He has been on the losing side just twice: the 2-0 defeat at Leicester in the Carabao Cup, when Liverpool looked lethargic generally and seemed to use the game as a training match for Philippe Coutinho, and the surprise 1-0 loss to Swansea City -- a negative, smothering performance from the home side meant Robertson saw a lot of the ball but he did little with it.
Perhaps this was the performance Klopp alluded to when he was praising Robertson after Porto for his crosses? Klopp also referred to what he regards as unfair treatment of Moreno in the past. That needn't ring alarm bells for those who want Robertson to keep his place.
Moreno has already been brought back, but Liverpool lost 3-2 in the FA Cup to struggling West Brom and he's not been seen since.
Cynics might believe Klopp is covering his own tracks, that Robertson was only given a longer chance because of injury to others. However the current situation came about, Robertson has improved the team and that's all that fundamentally matters.
With a resounding first-leg win in Portugal, Liverpool will surely have more two-game weeks in the near future and Moreno might have to play sometime. Klopp must keep all his squad players confident and eager, even if team selection probably becomes more consistent over the coming months.
Even when the Reds were beating Porto 4-0 late on, Robertson was still flying down the wing, sending in one perfect cross that Mane should have scored to get his hat trick earlier than he did.
Robertson proved he does have that attacking fervour Klopp demands from his full-backs and the energy to keep going till late in the game. His one real letdown was that Swansea game, which is forgivable in any new player. Liverpool should really have got something that night anyway, in which case Robertson's performance wouldn't have mattered.
He's 23, hardly a youngster in the modern game, and already had experience in the top flight, albeit briefly, at Hull. But he is one of Liverpool's transfer success stories.
In the summer of 2014 the Reds bought Mario Balotelli, Moreno and Dejan Lovren; in the past seven months they've bought Salah, Robertson and Virgil van Dijk. That, more than anything, sums up their recent improvement and the hope is there will be more to come next summer.