The 21-year-old, on the verge of becoming a Premier League champion adding to his European Cup, Club World Cup and Super Cup honours, went through gruelling preparation at Kirkby to morph from a midfielder to a right-back in order to break into the first team.
For three months, Inglethorpe and Neil Critchley, the Under-18s manager at the time, worked to enhance Alexander-Arnold’s mental and physical endurance as well as eliminate his petulance.
He would arrive on the training pitches with the best attacking players tasked with repeatedly running at him, isolating and beating the fullback in one-on-one situations.
But it wasn’t just that positional priming that has served Alexander-Arnold well under Jurgen Klopp.
During a lengthy exclusive interview with MR PORTER, which is released on Thursday morning, the Scouser touched on another important lesson.
“I want every trophy and as many of them as possible,” Alexander-Arnold said.
“I remember Alex Inglethorpe breaking it down into a thought process that I’ve never stopped thinking about since. It was when I was around 18 and he asked me ‘when do you retire? Maybe when you’re around 34 or 35. That’s 17 years.’
“And he told me, ‘so you’ve only got 17 attempts to win the Premier League, 17 attempts to win the Champions League or any other trophy. As much you think that’s a long time, the reality is you get only 17 tries and there will be failure, which is natural and will reduce that number.’
“I’ve been in the senior team fully for three seasons, the first try ended in a Champions League final defeat [to Real Madrid in 2018]. The second, we missed the title by one point, but became champions of Europe.
“This season, we’re close to winning the Premier League. So I’m already thinking I’ve only got 14 more chances. Even though you can play hundreds of games, the fact is you only get a few attempts at silverware.
“So, I really pour everything into each season and focus on the here and now. It doesn’t help to think about the future and winning five or six trophies or whatever because you’re then losing sight of the opportunity in front of you to do something special.
“I know that if you get into that relentless habit, with a great team, a great manager and a great support structure, the chances will automatically be maximised.”
In the interview with MR PORTER, Alexander-Arnold also discusses how his family have inspired the standout moments of his career thus far, the importance of giving back to his community and why it is imperative players use their platform to support Black Lives Matter to help force long overdue change.