That's because it is former Manchester City starlet Brandon Barker, who at 27 is currently a free agent.
Barker joined City when he was eight years old and made his way through the ranks to be on the cusp of the first team.
In 2014, he was named the academy Players' Player of the Year - a prestigious honour in a set up that has produced star names in recent years like Phil Foden and Jadon Sancho.
That same year he signed his first professional contract with the club, but it was while playing for the Under-21s that he caught Alexander-Arnold's eye.
The winger gave him a torrid time and he still carries those scars from the performance.
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When asked about the best player he played against who never made it to the top, the Liverpool full-back said: "I would say Brandon Barker, played for [Manchester] City.
"I was 18, playing for the Under-21s, first ever time at Anfield, got beat 3-0. He scored two and got an assist. I came off at 60 [minutes].
"Still to this day, he's the opponent I think that just destroyed me, man. I've never had it like that before.
"At that point, I'm thinking 'this kid is going to be the best player in the world'.
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"Because I'd never seen someone move so quickly and sharp and effectively, so I'd say Brandon Barker."
Barker has not lived up to that prediction from Alexander-Arnold and only made one professional appearance for City.
He had loan spells at Rotherham, Hibernian and Preston before joining Rangers permanently in 2019.
The winger's talent was evident to his teammates, even if he never quite showed it on the pitch.
"Brandon Barker. One of the best trainers I have ever seen,"ex-Rangers star Andy Halliday said.
"I know for a fact if you ask anyone who has played with him at any club - whether it's Hibs or Preston - they'd all say the same thing.
"Josh Ginelly when he came to Hearts, had played with him at Preston, and he said the exact same thing.
"He said: 'Brandon Barker was the best I've ever seen in training'.
"He was at Man City when he was younger and apparently he was the one coming through at Man City at that time.
"Honestly, in training he would get the ball off the goalie, dribble by the full team and score.
"I'm not saying people thought Brandon Barker was s**** but fans would say he's not good enough but in training..."
He played just 27 times for Rangers, but did get a 2020/21 Scottish Premiership title medal despite joining Oxford on loan halfway through the season.
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His contract was terminated by mutual consent in January 2022 and he joined Reading on a short-term contract until the end of the season.
Barker then went to Cypriot side Omonia, but was released just a few months later, despite facing Manchester United in a 3-2 Europa League defeat, and now remains without a club.