The Brumbies piled on four unanswered second half tries to secure a 38-11 bonus point win over the NSW Waratahs at Canberra Stadium on Saturday night.

The win sends Dan McKellar's side two points clear at the top of the Super Rugby AU standings, on 23 with two matches remaining, while the Waratahs' finals hopes are hanging by a thread.

The Brumbies could all but sew up a home final scheduled for September 19 should they beat the Western Force at Canberra Stadium on Friday night, while they also have another game in hand against the Queensland Reds.

But the Waratahs only have one more shot to put points on the board, clinging to third place with 15 points ahead of a clash with the Melbourne Rebels, who sit in fourth on 14 points with two games up their sleeve.

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Alaalatoa says the Brumbies will ride a wave of confidence into their clash against the winless Force - but stresses underestimating the nomads from the west would be a huge mistake.

"It's huge for us. With the way the game was going, I was really proud of how we came out in the second half," Alaalatoa said.

"We put on four tries and I was very proud of the way the boys continued to put on pressure. We've got a shorter turnaround now, it's all about our next job, next week, how we can grow as a group and be better.

"Off a win you always have a lot of confidence, but for us it's about reviewing ourselves hard and continuing to find ways to be better.

"You can't fall in love with yourself because that's where the trap is. The Force displayed some great passages last week and we know they're going to come here with nothing to lose.

"It's all about our next job, and just making sure we find ways to be better individually and collectively as a group."

Waratahs captain Rob Simmons is "very confident" his troops can bounce back against the Rebels at Leichhardt Oval on Saturday night.

Coach Rob Penney says there is simply no other option - they need to win or their title hopes go down the drain.

"It's a must-win isn't it? If we want to have a crack at getting in the top three, we've got to win next week," Penney said.

"You put the Waratahs jersey on, there's expectation aligned with that. The boys wearing the jersey are capable, there will be some learning going on.

"We do have to be able to combat good sides when they lift their intensity as the Brumbies did, and not capitulate in a couple of areas.

"The lineout was under a bit of pressure, some of our breakdown work wasn't where it needed to be. That can happen too, when you're playing catch-up. You get caught running when you shouldn't run, you lack a bit of support.

"We've got to be better."

AT A GLANCE

Super Rugby AU round eight: ACT BRUMBIES 38 (Tom Wright 2, Pete Samu 2, Ryan Lonergan, Andy Muirhead tries; Lonergan 2, Bayley Kuenzle 2 conversions) bt NSW WARATAHS 11 (Jack Dempsey try; Will Harrison 2 penalties) at Canberra Stadium. Referee: Angus Gardner.