Because just as Australian rugby clubs need to prove why they belong amid fears up to three Super Rugby AU franchises could be culled, the Brumbies proved they are fighters.

On this night it seemed as though they were destined to finish on the canvas. Noah Lolesio slapped the ground in agony before being helped to his feet and limping off with a hamstring injury.

Seated behind him on the sideline was a dazed James Slipper after he failed a head injury assessment, and to their left a yellow-carded Andy Muirhead, whose mistake had proved costly.

But somehow the Brumbies managed to overturn a 15-point deficit to secure a last gasp 24-23 win over the NSW Waratahs at Sydney Olympic Park on Saturday night.

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It was an unlikely hero sealing the deal in back-up scrumhalf Issak Fines, who sliced through a gap in the dying stages with poise beyond his years to cap off his second game in stunning fashion.

"I'm really happy. The Tahs were very good tonight, they're a good young side and I take my hat off to them," McKellar said.

"I feel for them a little bit to be honest, they played really well and it was a hard slog in tough conditions.

"We just dug in, we've spoken about that a lot, about those momentum swings against us and being able to deal with adversity."

This year's eventual champions will have something of an asterisk next to their names - or at least the letters "AU". But a case could be made to say four competition points have rarely meant as much as they do right now.

That is just what the Brumbies secured to move into second on the competition table after three rounds - keeping in mind they have had a bye wedged in between two victories.

Uncertainty hovers over the future of Australia's five professional franchises with New Zealand Rugby planning a new competition that will not cater to all of them.

How could a team dominating Australian rugby get the axe? It couldn't.

The Brumbies have recorded a profit in each of the past three seasons, all of which have been tumultuous at Rugby Australia headquarters.

They have reached the finals in all but one of the past seven Super Rugby seasons and are raging hot favourites to claim the Australian title this year.

And when the going got tough, the Brumbies rallied as one and they got going. Even when boom rookie Lolesio joined Wallaby Slipper on the bench.

Even when Muirhead was shown the cheese and referee Angus Gardner told Brumbies captain Allan Alaalatoa "if it happens again, someone is going to go" following six successive penalties.

Even after Tom Horton, a chippie from Mosman, pushed the Waratahs further ahead. After James Ramm scored down Muirhead's vacant wing. After the Brumbies bottled a chance to take the lead on the stroke of half-time.

"We had our backs against the wall for the whole second half, and when we needed to execute, we did," Alaalatoa said.

"[The tries just before half-time were] obviously very important, we only won by one point. We got unlucky there, we had a lot of pressure on them in the back end of the first half but didn't come away with points [on the siren].

"It was a good second half in terms of us fighting through that when our backs were against the wall."