The 22-year-old's new deal will keep him in Canberra until the end of the 2022 season, bolstering the club's depth in the No. 9 jersey behind Wallaby Nic White.

Now Lonergan has a chance to force his way into coach Dan McKellar's match day squad for a grand final appearance at Canberra Stadium on September 19.

It would be a dream way for the club junior to cap off a year which seemed at times like it would be derailed by the coronavirus pandemic and an untimely ankle injury.

But the former Junior Wallabies captain has bounced back to put himself in contention for a showdown with either the Queensland Reds or Melbourne Rebels in next week's decider.

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"It doesn't come around too often does it? To be at the club you've grown up watching is even more special," Lonergan said.

"I'm really excited to have the opportunity to be a part of the group that's going to play in the grand final.

"It's been tough [this year]. I never really thought about it, took it day by day and it didn't really rattle me too much. When I think about it, I've played stuff all footy this year for a lot of work.

"It's been a really disjointed year, but I try not too think about it too much. It has happened to everyone, it sucks not being able to continue the competition the way it started and to have to go into lockdown and lose our rhythm, but you can't really dwell on it.

"It's happened, it's gone, we're in the grand final and that's something to look forward to this week."

McKellar has a fair headache to contend with over the next few days as he looks to settle on a squad capable of delivering the domestic title to Australia's most successful rugby union franchise.

White started the Brumbies' last regular season clash, and a return to the starting XV would leave Lonergan and Joe Powell to jostle for a place on the bench while Issak Fines waits in the wings.

"It has obviously been very competitive all year, there are four quality nines here who could all do a job next week," Lonergan said.

"Whoever Dan decides to go with, I'm sure they will do a great job for the team. Whoever doesn't get picked will train their hardest next week to prepare the team as well as they can.

"[White] is one of the best nines in the world and he has been to a lot of big games throughout his career. He has a wealth of knowledge, and he has been open so far giving me hips and tips. I'm sure that will continue over the next two years.

"Joe has been awesome for me ever since I've been here, he's been here since I've been here and longer.

"He has been really good for me, really open, and he is one of my better mates throughout the team. We get along really well and he has taught me a lot over my career."

A grand final appearance would double as Powell's last hurrah for the Brumbies as the off-contract scrumhalf faces an uncertain future.

For Lonergan it would be the next step of a short career that has seen him emerge as one of Australian rugby's most impressive youngsters.