"Sonny wasn't playing this day, he had just finished weights and me and 'Milf' were like, 'That's Sonny'," he says. "We asked him if it was OK to take a photo."
"He said, 'We'll do it after the game and I'll come to your sheds'. We played, we got thrashed and we were like, 'He won't come now'. But he came into the lockers, asked for me and Milf, and we got our photo. He encouraged us to keep going.
"It said a lot about his character, for someone who had done so much in the game, and in union as well, and to come and see two young kids starting their NRL journeys ... it speaks so highly of who he is as a person. Nobody can fault how he plays and carries himself as a footballer.''
Papalii has since become one of the NRL's top middle forwards, resulting in 11 appearances for Australia and 15 for Queensland, and was a big part of the Raiders push towards a Grand Final berth in 2019.
In 2018, playing in his prime, Papalii still resorted to schoolboy fandom when he met Williams again, this time at a Blues training session at North Harbour Stadium. He got another picture, coupling it with the words 'star-struck' and 'goat' on social media.
"The Auckland Blues had just finished training and a lot of us had seen Sonny in a car on the way out. We were all on the bus up against the window and waving like little schoolgirls," Papalii says. "I'm not sure who sent a text, but Sonny came back and took a few photos with us. I think most players are still starstruck by him. I still am. It will be good to see him back in the NRL."
Williams is set to make his return to the playing field this weekend, when the Roosters face the Raiders in a Grand Final rematch. It will be his first game in the NRL since the 2014 Preliminary Finals.
Papalii describes the highly anticipated occasion.
"We're looking forward to the challenge, and Sonny will be someone we need to look out for," he says. "He'll still be dangerous. He's 35 now, but he's still got a rig like he's 21. Sonny's still got it."
"After last year's Grand Final loss, you start the year off by looking at when you play the Roosters. They've been the best side for the last five or so years. You always want to play against the best and make sure when you're up against the Roosters you're putting in your best game."