Butler has vowed to lift his game to a new level to replace former Wallabies captain Pocock, who faces up to a month on the sideline just one game into his return from two knee reconstructions.

Pocock's absence has paved the way for Butler to reclaim the No. 7 jersey for the Brumbies' round-two clash against the Waikato Chiefs in New Plymouth.

Vaea will come into the starting side for the first time in almost three years following the 26-year-old's battle to recover from life-threatening blood clots.

Butler was thrust into the job of replacing Pocock last year, stepping up to fill the 45-Test flanker's shoes and in the process joining a list of legends - including George Smith, Stirling Mortlock and Matt Giteau - as the Brumbies' best and fairest winner.

The 23-year-old says he's ready to rise to the challenge again, determined to ensure his role as a "fill-in" doesn't hinder the Brumbies' hopes of victory in New Zealand.

"Obviously Poey is a leader, but I want to contribute as much as I can around the field because we don't want to lose anything," Butler said.

"This is a new year so I want to start fresh. Poey got man of the match in his first game back … my job is to make sure the team doesn't lose anything by not having him there.

"I'm a little bit more comfortable with the role now, not as nervous as I was last year. I was absolutely nervous last season, stepping into Poey's shoes was always going to be a huge task. But I hope last year has helped me prepare for this."

The Brumbies will announce their team on Thursday, with minimal changes expected for the 2013 grand final re-match and a mouth-watering contest against cross-code star Sonny Bill Williams.

Vaea made a shock comeback to Super Rugby last week and his journey back on to the field will be complete when he's included as the Brumbies' No. 8 to take on the Chiefs.

Vaea was told he would never play again when scans discovered blood clots on his heart in 2012.

But an injury to Fotu Auelua, impressive pre-season trial form and a physical performance for the Brumby Runners last weekend has convinced the Brumbies Vaea is ready to restart his career.

"Ita's just that little bit more aggressive and that's what makes him so attractive to the coaching staff," said Brumbies collision coach Peter Ryan.

"He's got mongrel, he's definitely got it. It's not that others don't have it, he's just got that little bit more. Guys want to play with him, he can turn it on when he walks across the white line and be aggressive in everything he does."

Pocock suffered an ankle syndesmosis injury in an 80-minute performance against the Reds.

Despite playing just five games in the past two seasons, Pocock was back to his brilliant best and effected four breakdown steals before being injured.

But Butler wants to pick up where Pocock left off, intent on adding a hard edge to his breakdown skills to disrupt the Chiefs' attacking flow.

"I worked during the National Rugby Championship at having a presence at the breakdown, I've been doing a lot of work with Dan McKellar and Peter Ryan," Butler said.

"It's something I want to bring into my game, but it's a bit opportunistic as well. Hopefully those opportunities present themselves and I can capitalise on them. As long as you rip in and put your head in there, you never know what will happen."

SUPER RUGBY ROUND TWO

Friday: Waikato Chiefs v ACT Brumbies at New Plymouth, New Zealand. 5.30pm. TV time: Live on Fox Sports 2.