Earlier this season, Jurgen Klopp was asked which of his current players he's been most surprised by in terms of progression since his arrival at the club in 2015.
Trent Alexander-Arnold was his answer, as he stated: "I have known him since he was 17 years old. He was a big talent but we were not sure he could do it physically. Now he is a machine – so he is a big surprise.'
The Liverpool boss made a direct reference to his physical capacity, but it's reasonable to suggest that his offensive output on the pitch will have impressed the German even more so.
With the Premier League campaign currently on pause, let's reflect on what Alexander-Arnold was, what he is right now, and what he may become in the future from a tactical perspective.
The attacking contribution that Alexander-Arnold is presently renowned for wasn't particularly demonstrated three years ago.
The academy graduate stepped into the first-team and performed a relatively functional role. He was very much a traditional full-back while sporadically demonstrating his hidden passing ability.
Alexander-Arnold made seven Premier League appearance in the 2016/17 season, with three of those being one-minute cameos against Middlesbrough, Tottenham and Arsenal.
His full debut was notably handed to him at Old Trafford, with his passing network pictured below.
It's more daring than many would expect from a teenager making his full senior debut away to Manchester United, but it still doesn't offer much of an insight into what he's currently doing for the Reds.
The present version of Alexander-Arnold is considered amongst Europe's elite. His offensive contribution from full-back is mostly unrivalled, as captured below.
The scatter plot includes every player from Europe's top five leagues who's amassed over 1,500 minutes as a full-back this season. Their attacking performances have been judged based on shots assisted per 90 which highlights quantity, and open-play Expected Assists per 90 which covers quality.
Evidently, Alexander-Arnold is demonstrating both quality and quantity when generating scoring opportunities for others. He's outperforming every one of his peers to such an extent that speculation has emerged as to whether his future lies in midfield.
His passing network from a fixture earlier this season against Spurs is pictured below, and it's evolved significantly from his debut clash with the Red Devils.
The English defender is now almost redefining the concept of a full-back, so how will he be performing in another three years' time?
Whatever role he's fulfilling, he has to be able to impose himself on the game from the right of the pitch with his offensive qualities and his passing range.
The answer to his future position ultimately depends on the tactical development of Liverpool as a squad.
If Klopp wants to retain the industry that he's managed to establish in the centre of the park, then Alexander-Arnold is unlikely to move, whereas if the Reds are to adapt, perhaps Alexander-Arnold could perform in a similar manner to Manchester City's Kevin De Bruyne, as an advanced no.8.
How Liverpool will develop in a tactical sense, and how good Alexander-Arnold will become are the two crucial unknowns that will determine whether he masters the art of defending despite being a full-back, or whether he matures to become a more central presence.
Regardless, it's likely that Alexander-Arnold will be even more decorated once 2023 comes around.