The former Australian under-20s back-rower insists Canberra is the best place to challenge himself and will sign the first multi-year contract of his career.

The Brumbies will invest in Butler, who has capably filled the void left by Pocock, and Nigel Ah Wong, who comes with a recommendation from Test coach Ewen McKenzie, to add depth to their Super Rugby squad.

Butler will sign a two-year deal after impressing in his first season with the Brumbies, while winger Ah Wong has been playing with the Tuggeranong Vikings and will get his Super Rugby chance next year.

Pocock played just three games before rupturing his anterior cruciate ligament for the second time in 12 months, opening the door for Butler to stake his claim for a regular spot.

The 22-year-old has been rewarded with a starting spot in every game this year, and says his challenge next year will be having the same impact with a fit Pocock back on deck.

“It’s been awesome to have that extra responsibility … I don’t know how it’s going to work next year and at the moment I’m just trying to get confidence playing Super Rugby games," Butler said.

“I was nervous about coming down here. There are some of the best back-rowers at the Brumbies and it’s a challenge, but you learn at the same time as well.”

The Brumbies are in the middle of a recruiting and retention spree.

In the past three weeks they have re-signed Butler, Matt Toomua, Christian Lealiifano, Jesse Mogg, Nic White and Allan Alaalatoa. They have added Ah Wong and Tom Staniforth to the 2015 roster, with at least one more new recruit to emerge in the coming weeks.

Wallabies winger Joseph Tomane, who is out of action with a busted eye socket, is in negotiations to stay, while powerful No. 8 Fotu Auelua is also considering his future and wants to stay with the Brumbies.

Coach Stephen Larkham said the Brumbies were in no rush to finalise their roster and would use the inaugural National Rugby Championships to scour Australia for more talent. The NRC starts in August with the Canberra Vikings to act as a breeding ground for Brumbies players.

“We’ve got the core and base of our squad together now and that’s very pleasing that we’ve been able to keep those guys for four years,” Larkham said.

“We’ll use the NRC, it’s there to develop some talent and we’ll wait to see how guys play in that to make some decisions on positions.”

The versatile Ah Wong played with Butler as a junior in Queensland, but spent last season in Japan.

He started his career as a flanker, but the Brumbies have recruited him as a 100-kilogram winger with lightning speed.

“He’s big and he was a forward so he’s used to the tough stuff at the breakdown, which is what our wingers are used to,” Larkham said.