There was once a time when Josh Addo-Carr and Valentine Holmes were setting Shark Park alight in one of the paciest under-20s backlines ever assembled.

Come Wednesday night, their speed could help decide a State of Origin series.

Queensland confirmed on Tuesday that Holmes will shift from fullback to left wing for Wednesday’s decider at Suncorp Stadium.

There he’ll be given the task of shutting down Addo-Carr, whose speed turned Origin II and made Nathan Cleary’s early kicks so valuable.

The pair have marked up on each other previously in the 2018 Origin, but their playing days go way to 2014 when they were teammates at Cronulla.

“He was just one of those kids who was going straight to first grade, and everyone wanted to be in his position,” Addo-Carr told AAP.

“He was such a good player.”

Holmes was the star of the team, kicking goals and leading the points-scoring after collecting 14 tries in 15 games before making his NRL career.

Addo-Carr was the fresh face picked up by then-Sharks 20s coach James Shepherd, seizing his chance to top the try-scoring charts with 17.

“Someone got injured in the first game, I was 18th man, the coach ended up putting me in and I cemented my spot,” Addo-Carr said.

“I played everywhere. Fullback, wing, centre and a bit of five-eighth too.

“I was definitely a lot lighter and a lot fitter back then too.”

Shepherd still regards Holmes and Addo-Carr as his two best finds, with Holmes spotted off video from Townsville and Addo-Carr from a trial after a tip off about his speed.

Shane Flanagan’s first-grade ban meant he never coached them together in under-20s, but he has since watched them score a combined 16 tries in 14 Origins.

“They’re both so gifted. When you see those boys play in juniors, they just stand out,” Shepherd said.

“They are extremely fast. Josh is the fastest kid I have ever coached and Val is not far behind him.

“I coached (Addo-Carr) in 2015 when Shane came back, and in a team that struggled, Fox was exceptional.

“Val was just a shining light. He was one of those players from his first run to his last he didn’t drop any speed.”

But for all the hype about their pace, Shepherd knows it will be more than just sheer speed that decides their battle on Wednesday night.

“They’re not just sprinters, they are footy players,” Shepherd said.

“They sense opportunities and they can beat people and score tries that others can’t.

“And that’s why they are where they are. They’re the elite of the game.”