And, at 6ft 9in, the Glasgow Warriors lock forward certainly cuts an imposing figure.
Still only 18, Samuel will lead the side into the rearranged tournament which begins later this month and will be played in its entirety at Cardiff Arms Park.
The young Scots kick things off in the opening match against Ireland a week on Saturday and Lineen expects Samuel to rise to the occasion.
“He’s a top young man,” said Lineen, the Scotland U20 coach. “I’ve been really impressed with his attitude. I’m not going to pump his tyres up too much, but we’ve got a really good partnership there with young Max Williamson.
“We’ve lost Jamie Campbell, who was the senior lock, so these lads have another year at under-20 and this is a really good opportunity to shape them both. They are on senior academy contracts with Glasgow already and I know Danny Wilson has been impressed by both of them.
“I’m expecting big things from Alex and it looks like he has taken the captaincy in his stride at the moment.”
Samuel is highly regarded and was invited to train with the full Scotland squad during the Six Nations, an opportunity he seized.
“I just got in there and tried to soak up as much information as I could and learn from the best and then tried to bring that back into this 20s environment to push the standards up,” he said.
“It was like everything I have done before, just at a higher standard, everything was done to time and it was very exact and it was a really good experience.”
Hailing from St Andrews, Samuel got his first taste of the sport with the minis at Madras Rugby Club then continued his development in the team at St Leonards school before being included in the 2020/21 intake for the Glasgow FOSROC Scottish Rugby Academy.
He said he would love to play in the back row and even had a stint at stand-off at school but is realistic enough to know that he is destined for the boilerhouse.
“I started at Madras Rugby Club in primary, there is a really good set-up down there with dads who coach. I have always kind of been a second-row, in first year, second year, third year I played a bit in the backs, 10 and a bit of 12, but I was always going to end up in the second-row as I have always been tall.”
He is hoping to get a taste of action with Glasgow Warriors next season and has been encouraged by the club’s willingness to give young players a chance. In the meantime, he is itching to get out and play in Cardiff after a season without competitive games.
“Everyone has been so excited to get back in and get going, especially the senior academy guys who have done a season training and haven’t been able to put that into practice. We are all raring to go.”
After Scotland U20s’ opener against Ireland they will play England on June 25, Italy on July 1, France on July 7 and Wales on July 13.