Then his debut under duress as an 18-year-old with a grade three AC joint injury proved he had the mettle to shine in the toughest arena.
On Sunday in the 19-18 grand final win over Newcastle, a week after returning to action in record-equalling time from a syndesmosis injury, Walker realised a dream and honoured the legacy of Keary, who won the 2018 and 2019 titles at five-eighth with the Roosters after his premiership at South Sydney in 2014.
Walker, who said he intended to stay at the Roosters long-term, had further reason to celebrate on Monday when named in Australia's squad for the World Cup where he is on track to make his Kangaroos debut.
Walker, now 24, emerged from the Brisbane Broncos Academy but a chat with Keary in Sydney crystallised in his mind that the Roosters was where he would play his best football.
"Luke Keary was enormous for me, especially early on," Walker told AAP.
"He is such a good man first and foremost and really helped me settled into the club.
"Off the back of that, I played alongside Luke and learned as much as I could off him. I will always look back on that as a special time.
"He was a three-time premiership winner and knows how to get it done on grand final day.
"For me to now win a premiership here at the Roosters is a dream come true. We had fallen short for a couple of years now but there was so much faith and belief we could get the job done."
Walker said his ankle was "pretty sore" after he played with great control and composure in the grand final. He returned from a 27-day absence to play in last week's 36-20 win over the Dolphins in the preliminary final, a week earlier than his father Ben Walker thought was possible.
Ben told AAP his son's toughness was unquestioned.
"He's a tough kid. I thought he'd be back for today but not for the prelim," he said.
"When Sam made his debut he had suffered a grade three AC joint injury the week leading up to it and had to get a needle.
"Anyone who has played knows how painful it is.
""He didn't sit out but embraced the opportunity to play and said, 'I will get through it'. He played for 21 games straight with needles.
"His mum Kylie is a tough woman and her mother was really tough.
"She could have died eight times but kept battling away with certain conditions that she had but she never gave in and was a real fighter."
Ben, who won a premiership with the Broncos in 1997, said Sam's win in the grand final was a great occasion for the entire family.
"He has been a Roosters supporter all his life. He's watched them win grand finals and came here to the club after they'd just won two," he said.
"He applied himself to get to this day. To win is enormous. \We are really proud of what he has done."
Walker has shown great courage to get through tough times and prevail.
"He did an ACL in 2024 when they were going really good, got back and then last year they stumbled and didn't get into the top four," Ben said.
"I hope he enjoys this one. It might be his last."
Sam said the Roosters' motto of "we play for premierships" had resonated with him.
"They know what they want and we have to go out and deliver it," he said.
"The Roosters give you a helping hand every step of the way."
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