Mann-Rea and Holmes are set to get a chance to shine when most players their age are ending their careers, as they aim to replace injured Wallabies captain Stephen Moore and target a finals berth.

Mann-Rea is the 33-year-old, eight-game rookie who's the oldest and most inexperienced player in the Brumbies' full-time squad.

When Mann-Rea, known as Bongo to his teammates, was on a $40,000 extended player squad contract last year, and snapped the anterior cruciate ligament in his knee, he was ready to give up on rugby and return to working in the mines.

Holmes, 30, is a former plumber and Super Rugby journeyman. He has 26 Super Rugby caps from playing at the Western Force, Melbourne Rebels and NSW Waratahs. He will juggle work at his clothing brand and as the Warringah Rugby general manager with Brumbies training.

Their respective records pale in comparison to 92-Test and 131-Super Rugby caps Moore. But Mann-Rea was unfazed by the challenge of replacing a star.

"A couple of years ago when I finished in Japan, I thought that was it, I was done. Then I did my knee last year and I thought that was it again, the end of the career," Mann-Rea said.

"But now I'm looking at getting a chance to start my first game for the Brumbies. When you lose a guy like [Moore], there's always going to be the perception we'll be weaker without him.

"I'm not trying to be Stephen Moore. I'll just try to do what I can for the team and, hopefully, we can achieve the goal we set for the season."

Holmes arrived in Canberra on Tuesday for his first training session with the Brumbies.

His work and family commitments in Sydney mean he won't be able to commit to a full-time move to the capital.

But it is likely he will return to Brumbies training over the next month in preparation for the crucial clash against the Waratahs on June 28.

Holmes quit rugby last year. He wanted to have a "normal life", spend more time with his wife and three children, become Warringah's general manager, play club rugby in Sydney with his brother Josh and invest more energy into his clothing label.

"I worked jobs while I was playing rugby anyway, I had to do 'normal world' stuff right when I was starting my rugby career," Holmes said.

"If the opportunity comes and I'm lucky enough to get a crack ... I'll just stick my head down and learn as much as I can.

"Moorey is the Australian captain, he's led the way for hookers in Australia for a decade, they're pretty big shoes to fill."

Mann-Rea trained with Moore at the Queensland Academy when he was starting his career, and played alongside Matt Giteau and Mark Gerrard in the Australian junior teams.

Mann-Rea said he threw away his opportunities and found himself working in the Wollongong coalmines while Moore, Giteau and Gerrard established themselves as international stars.

He gambled on revolutionary ligament replacement surgery last year to save his career and Mann-Rea wants to repay the Brumbies' faith.

"It's funny how things work out," Mann-Rea said.

"There's a fair bit of responsibility on myself to fill those shoes and hopefully get to the finals.

"I feel like I'm ready to step up and get the boys over the line."