Walker is 78kg wringing wet, but his durability to play through a grade-two AC joint injury in his debut season in 2021 proved he is far from wet behind the ears.
The injury usually keeps players out for at least four to six weeks, but 22 needles in 21 games got Walker through.
The 23-year-old will play his first State of Origin match on May 27 in Sydney with a Maroons-tough history that has him in good stead for the cauldron.
Sam's father Ben Walker, who enjoyed a wonderful NRL career, has shed light on his son's mettle with a recollection of his debut year for Sydney Roosters.
"In Sam's first NRL game when he had just turned 18 he had done his AC joint the week before and didn't really say too much to the club because he knew he was going to get his debut the next week," Ben revealed.
"So he got needled every single week that first year, and in one game he got a needle at halftime as well.
"To be needled for your debut game and to get through it and not complain about it just shows how tough and resilient he is and that he's built for this (Origin) level because it's a far greater level than week-to-week NRL game."
A ruptured ACL at the end of 2024 was another blow, but one that also led to growth.
"I had to start again the following year, but it has made me a better footballer and given me an understanding of myself," Sam said.
Walker's attack is so good that an urban myth has developed that his defence is not up to the mark.
He has missed less tackles than many NRL halves this year, including legends Nathan Cleary and Cameron Munster.
Maroons great and selector Darren Lockyer rubbished suggestions that Walker's defence was an issue.
"I remember when I played, people questioned my defence too," Lockyer said.
"It just motivates you to want to be better at it. I suspect with the talk around Sam and his defence ... that will be a real focus for him."
Walker chuckled when it was put to him that Roosters teammates and NSW foes Victor Radley and company would be gunning for him.
"I am sure it will be exciting for them," he grinned.
"It is a side of the game I am continually improving."
Family connections are strong with Sam, so it was a special moment when he was out to dinner with his parents, uncle Sam Walker and other family members when coach Billy Slater called on Sunday night.
On the menu was a giant whole fish and a tomahawk steak, which tasted even better after Slater's call.
"We were all in tears. It was pretty emotional," Ben said.
"We all had a hug. I'm just very proud of Sam. People who have been with him for so long understand the sacrifices and determination that it takes to get to this level.
"For him to go and live running out for Queensland will be very, very special."
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