But referee Rasta Rasivhenge's decision in the final minute of a five-point loss will haunt them for the next six months after he incorrectly awarded a scrum to the Waikato Chiefs, handing them a 24-19 triumph.

Former Wallabies George Gregan and Stephen Hoiles joined Brumbies coach Dan McKellar in questioning why Rasivhenge didn't use the television match official to get clarity on the costly last-minute decision.

Chiefs second-rower Tyler Ardron attempted to intercept a Brumbies pass just 22 metres from his own line. He was never in a realistic position to catch the ball, which is regularly punished by being sent to the sin bin.

Rasivhenge made the mystifying decision to rule a knock on against the Brumbies, didn't penalise the Chiefs and then refused to check with the TMO to get the right outcome.

It effectively ended the gutsy Brumbies' faint hopes of a finals berth, and was compounded by a first-half error from Rasivhenge to disallow a Folau Faingaa try because of a forward pass.

The TMO can rule on forward passes in rugby, but Rasivhenge stood by his decision on the field.

"It looked like a knock on [at the end]. I've only looked at it quickly, but I don't know why we don't check those [with the TMO]," McKellar told Fairfax Media.

"The [try] that got disallowed in the first half for a forward pass, to me that didn't look forward. Why not let him score the try and just check it?

"We use the TMO for everything else, why didn't we use him tonight? We're disappointed. But we look back and we made too many errors, we didn't turn up from the first minute thinking we could dominate.

"We did that in the second half and that's learning for this young group. The learning is to turn up from minute one, roll up the sleeves and get the job done.

"You can't come here, turn over so much ball in 40 minutes and be off around the collision area and expect to win. But I'm so proud of that second-half effort."

The Brumbies were sweating on a result in a South African derby on Sunday morning to determine if they were still a chance of making the finals.

They needed the Cape Town Stormers to beat the Durban Sharks to give them any hope of staying in contention with one game left in the season.

If the Stormers won, the Brumbies would need to beat the NSW Waratahs with a bonus point and have the Melbourne Rebels and Sharks lose their last games by more than seven points.

It will be only a small window of opportunity, but the Brumbies showed enough brilliance in attack in the second half against the Chiefs to prove they're capable of something special if things go their way.

"I'm incredibly proud of our effort. I thought we had belief right to the end," said David Pocock said.

"But against a team like the Chiefs, a few lapses and they punish you. They’re an incredibly classy team."

The Brumbies trailed 24-5 with 15 minutes to go and looked dead in the water when Joe Powell threw an intercept pass, allowing the Chiefs to go 95 metres to score at the other end.

But that sparked the Brumbies into action, with Tom Banks and Henry Speight scoring when Jesse Parete was in the sin bin and then the visitors launched one last attacking raid in the last 90 seconds in the hope of keeping their season alive.

The Brumbies marched from inside their own 22 metres to the edge of their attacking zone when Ardron knocked down a Wharenui Hawera pass. Pocock asked for it to be reviewed, but his request was denied.

"We keep coming back to TMO's and referees. The Brumbies lost it in the first half, that's a fact," Gregan said on Fox Sports.

"But that moment [at the end], that's where you want technology to stop what in other codes they call a howler, because that was a howler of a decision."

Hoiles, also a former Brumbies captain, added: "I think you say firstly that the Brumbies have themselves to blame.

"But you don't like to talk about decisions at the death that are incorrect. The situation is that was the wrong call on the bell. David Pocock tried to get the referee to go upstairs and have a look.

"I find that really frustrating that we've got the technology, we all saw it, but we don't use it at the end of the game."

Brumbies co-captain Sam Carter (back) made his comeback in Canberra's club rugby competition on Saturday and could be available to play the Waratahs, but the team will assess Tom Cusack after he was left bloodied after a nasty head knock against the Chiefs.

AT A GLANCE

WAIKATO CHIEFS 24 (Nathan Harris, Damian McKenzie, Johnny Fa'auli tries; Damian McKenzie penalty, 3 conversions) bt ACT BRUMBIES 19 (Henry Speight 2, Tom Banks tries; Wharenui Hawera conversion) at Hamilton Stadium, New Zealand. Referee: Rasta Rasivhenge.