Ben Walker expected his son to return for the grand final, but not the preliminary final a week earlier.
Sam Walker came back from a syndesmosis injury after 27 days out, then helped the Sydney Roosters beat Newcastle 19-18 on Sunday to claim the premiership.
The 24-year-old had also returned in record-equalling time, featuring in the Roosters' 36-20 preliminary-final win over the Dolphins.
His father said Sam's debut at 18 came after he suffered a grade three AC joint injury the week before and needed an injection.
"He's a tough kid. I thought he'd be back for today but not for the prelim," Ben told AAP.
Sam, who came through the Brisbane Broncos Academy, said an early conversation with former Roosters playmaker Luke Keary helped convince him to join the club.
"Luke Keary was enormous for me, especially early on," Walker told AAP.
Keary won premierships with South Sydney in 2014 and the Roosters in 2018 and 2019.
"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.
Ben, a 1997 premiership winner with Brisbane, said Sam's 2024 ACL injury and the team's struggles the following year had made the victory especially meaningful.
Walker said the club's motto, "we play for premierships", had shaped his outlook.
"They know what they want and we have to go out and deliver it. The Roosters give you a helping hand every step of the way," he said.