The Brumbies wanted to send the exciting 20-year-old prospect to play with the Southland Stags to gain valuable experience.

But the ARU stopped the move from happening to improve the standard of Australia's own second-tier competition, the National Rugby Championship.

Staniforth will now play with the NSW Country Eagles after the Canberra Vikings had already allocated all of their 14 Super Rugby contracted spots.

Brumbies Director of Rugby Dan McKellar said the ARU was within its rights to keep the best up-and-coming talent in Australia.

"We wanted to send Tom to play in the ITM Cup in New Zealand, but it was knocked back by the Australian Rugby Union at the final hurdle," McKellar said.

"Understandably, we're trying to develop our own ITM Cup with the NRC and they decided it wasn't the best move.

"It would have been good experience for a second-rower to play over there."

Staniforth captained the Australian under-20s last year - a month after making his Super Rugby debut for the Brumbies.

He has spent this year developing his game in the John I Dent Cup, and will play for Canberra Royals in Saturday's grand final against the Tuggeranong Vikings.

The NRC is in its second year and aims to fill the gap between club rugby and Super Rugby, similar to New Zealand's ITM Cup and the Currie Cup in South Africa.

The Brumbies spotted several players, such as Jordan Smiler, Rory Arnold and Joe Powell, on the back of the NRC last year.

"I think it's a great competition and ideally it's here to stay," McKellar said.

"It's a true pathway for club players to push their claims for professional contracts.

"To be realistic, we're not at that level yet in terms of (the NPC and the Currie Cup), but over time we'll get there."

The Tuggeranong Vikings provide nearly half of the Canberra Vikings' squad.

Eighteen players are from the Tuggeranong Vikings, while Royals have only three representatives.

Five players - three from the Gungahlin Eagles and two from the Queanbeyan Whites - are unavailable through injury or work commitments.

"When we named the club train-on squad, there was some discontent around how many Vikings players were in the team," McKellar said.

"As I said at the time, they've won four competitions in a row and the squad mirrors that.

"There's a couple of development players as well who have played Australian under-20s and we want to see how they step up to that high level of competition."

Those players are prop Tyrell Lomax - the son of former Raiders prop John Lomax - and hooker Connal McInerney.

Scrumhalf Michael Dowsett and lock Sam Carter will also play with NSW Country, while prop Scott Sio is with the North Harbour Rays.

Hooker Josh Mann-Rea and outside back Robbie Coleman will both miss the NRC to recover from injuries.