The ACT Brumbies' back-row was on fire. Rob Valetini is in career-best form, Jahrome Brown hadn't skipped a beat in his return and Pete Samu was as menacing as ever.

Now the 20-year-old flanker could find himself starting in a Super Rugby AU grand final against the Queensland Reds at Lang Park on Saturday night.

Reimer made his debut in a gripping qualifying final win over the Western Force this past weekend, coming on the cover for Samu who was felled by a knee injury.

The Brumbies are sweating on injury updates for Samu, James Slipper and Folau Fainga'a. The latter is expected to be free for this week's showdown against the Reds while Slipper is managing a recurring knee injury.

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No. 8 Samu perhaps poses the biggest concern after he was left on the Canberra Stadium turf clutching at his left knee. Rob Valetini looms as the man most likely to fill that position if needed.

Injuries to Brown, Samu and potentially Tom Cusack open the door for someone else to fill the No. 6 jersey, with Reimer confident he can step up to the plate if called upon in just his second Super Rugby AU match.

"Hundred per cent. It's obviously going to be nerve-wracking, in front of about 50,000 people or however many they're going to get," Reimer said.

"I have no doubt I will be ready to take on that challenge and do my role, execute my role and be a part of the team.

"It's something I wouldn't have thought about two weeks ago to be honest. I was that body in the tackle suit and had a few blokes in front of me. I'm looking forward to it, I just need to prep well and give every shot I can to putting that jersey on.

"The first probably three or four games, the back-row was on fire. Jahrome was just killing it, every single game he was putting everything in and just playing unreal. Bobby is still going unreal. He is yet to fault, yet to have a bad game, and Pistol is always consistent.

"There were a few moments when I thought 'I'm going to be wearing this suit for quite a while'. But I'm happy I'm finally there and proud to be a Brumby."

There is little doubt Reimer can handle the pressure of big moments. With eight minutes remaining in the qualifying final he earned a crucial turnover which allowed the Brumbies to kick nine points clear.

"We needed it. That put us out by nine, that turnover," Brumbies coach Dan McKellar said.

"He's a young bloke who has been patient and worked hard. You can sit there at training from one day to the next and think 'jeez, I'm not going to get a crack here'.

"Then all of a sudden he's debuting in a semi-final. He has been excellent for his club, he got half a dozen of those turnovers last week against Vikings [while playing for Wests in the John I Dent Cup]."

McKellar could be forced to field a somewhat inexperienced back-row in the decider against the Reds, depending on the availability of Samu and Cusack.

Brown's domestic campaign is over due to a shoulder injury, leaving Valetini to lead the charge alongside rookie Rory Scott, Reimer, Will Miller and injury cover Henry Stowers.

But McKellar has little doubt whoever he calls on will be ready to rise to the challenge as the Brumbies chase back-to-back domestic titles.

SUPER RUGBY AU FINAL

Saturday: Queensland Reds v ACT Brumbies at Lang Park, 7.45pm. Broadcast: Live on Stan Sport and 9Gem. Tickets from Ticketek.

*The Brumbies are offering a package for fans including a charter flight to and from Brisbane, a ticket to the final, and one night's accommodation. Secure your seat here.