Lucas was an experienced member of the Reds when Alexander-Arnold progressed from the Academy set-up to first gain a taste of a senior environment.
After making a professional debut in October 2016, the No.66 has gone on to lift six major honours with his boyhood club, establishing himself as one of world football's brightest talents in the process.
Recalling when he first encountered Alexander-Arnold, Lucas told Liverpoolfc.com: "He was very shy and very thin, I would say. He's a lot stronger now than when I first met him.
"But we could see Trent was special, even at 16 years old. We could see that he was different to other players – the way he used to work.
"I remember he stayed one year with us without playing a game but every day going to the gym before and after the training sessions.
"He had the patience to prepare himself because we knew as soon as he had the opportunity to play, he wouldn't be able to rest much.
"His improvement has been amazing and he's a world-class player now. Every season he is getting better.
"Now it seems that he's playing in a different position, so it just shows how much he can help the team with his qualities if it's in midfield or as a full-back. It's amazing to see how much he grew."
Indeed, Alexander-Arnold finished the 2022-23 campaign with Liverpool in a hybrid role that saw him moving into midfield when in possession and then returning to full-back without it, before he impressed on the international stage for England last month while solely playing further forward.
"He's a play-maker," Lucas continued. "Just see how many assists and goals he provides every season. He fits in because he knows how to move himself.
"Of course in midfield maybe he will have more players pressing him, maybe you have less time with the ball. But with his qualities, he normally plays one touch, two touch.
"He showed again with the national team what he's capable of doing. Last season he played kind of midfield but going to full-back for defending.
"He's another option for Jürgen. If you have a player that can play many positions, it just helps because at some point of the season Jürgen will feel that he can be used in midfield and it will be a chance for Trent to keep showing his qualities."
Off the pitch, Alexander-Arnold was voted into the Reds' leadership group within the squad back in 2021.
But with the recent departure of a number of established figures, Lucas feels the upcoming campaign presents the ideal opportunity for the Scouser to further enhance his standing as a leader.
He said: "He's a winner. He's young still but he's already a leader. He's been playing five, six seasons as a starter.
"Millie and Bobby left, so he will now step up, for sure, and become one of the leaders of the team – not just because of his quality but also because of his presence as well and what he's done for the club in the last few years.
"It will be another good season for him to keep growing and keep improving as a player, as a leader, as a man. I think it will be important."