However, the 20-year-old rookie – who worked in the club shop last season – came off the bench to score the decisive try in their 22-20 win over Wigan Warriors.
“I got told a couple of weeks ago I’d probably be 18th man for both the St Helens semi and the Grand Final,” explained second-row Walters. “So, I told my family there’s no point in them really coming as I’d just be running the cone on. There’s only my mum, little brother and girlfriend here.
“My grandma’s not got Sky so she’s just texted me – she’d been following it on Twitter.
“I got told I would be playing on Tuesday. I was shocked and I’ve been nervous ever since.”
Walters, who only started playing rugby league in 2013 after switching from Leeds Carnegie, benefited after injuries to three second-rows and when Brian McDermott left out teenage stand-off Jordan Lilley who had been on the bench for the last two games.
He scored with only his second touch after entering his first Grand Final in front of a sell-out 73,512 crowd at Old Trafford.
“Mac said to me before the game that there was literally going to be a scenario where I get on and maybe we’d be drawing or down and all he’d need me to do is work from marker and make my tackles,” said Walters.
“But I think I’d already made a mistake, slipping off (Matt) Bowen when he went under the sticks, so I was just thankful Jimmy (Keinhorst) could put me in position and I got over the line.
“I wouldn’t even say it was a dream. This year I’ve hardly managed to break into the team – it’s such a good side and there’s players above me like Mitch Achurch, Stevie Ward and Jamie Jones-Buchanan. It’s been so hard to even get in and at points I’ve been thinking ‘Wow, I’m not even going to get a game this season’.
“I’m just thankful Mac had faith to pick me and actually put me on as there’s been a couple of times where I’ve been in the squad but never got off the bench.
“I don’t even know if it’s sunk in yet – to get a try in a Grand Final at Old Trafford for Leeds Rhinos, it’s mad really. I’d only scored once before all season.”