The Brumbies kept their Super 14 semi-finals hopes alive with a spirited 27-21 victory over South Africa's Sharks at Canberra Stadium.

It was the first loss of the season for the Durban side.

Trailing 18-7 at halftime, the Brumbies' season looked over, but strong defence and ill-disciplined play from the South Africans allowed them back in the game.

Referee Bryce Lawrence warned the Sharks on several occasions and sin-binned two of their players for periods during the second half.

The game turned almost from the restart with the Brumbies' defence much stronger than in the first 40 minutes and their attack finally sparked.

Wallabies fullback Adam Ashley-Cooper, under an injury cloud during the week, returned to his finest form with two tries while fullback Mark Gerrard kicked five from five attempts.

The Brumbies' third try was scored by No.8 Julian Salvi during one of the periods the South Africans were reduced to 14 players.

The Sharks will likely retain second spot on the ladder behind the Crusaders while the Brumbies' victory keeps them in contention but the run to the semi-finals is exceptionally tough for the Canberra team.

The ill-disciplined play of the South Africans during the second half cost them the game with a string of penalties for infringements at the ruck, particularly offside clearly irritating referee Lawrence.

At one stage he gave Sharks captain Johann Mueller "20 seconds to talk to your team" after a series of infringements.

Whatever Mueller said clearly had no impact as within a minute the referee had sent Francois Steyn to the bin for 10 minutes for another foul.

A spirited crowd of 13,784 cheered the Brumbies home in the second half on a chilly Canberra evening in a week in which ACT Rugby announced that coach Laurie Fisher's contract would not be renewed next season.

Fisher praised his players for a "fairly stunning performance" in the second half but downplayed suggestions that the announcement of his coaching had played any part in the second-half revival.

"They did it for themselves, it was an achievement for the whole group," Fisher said.

"It was a courageous second-half for us. What we talked about at halftime was working en masse, not as individuals."

Fisher said he had urged his players in the second half to take the game up to the Sharks, particularly at the breakdown.

"Rugby is a game of momentum and self-belief - our self-belief never wavered."

The Brumbies have a difficult run to the semi-finals with a home game on Anzac Day against the Lions followed by a three-week trip to South Africa and Western Australia.

Sharks coach Dick Muir was scathing of his players' second-half performance.

"It was stupid play on our behalf, we gave away too many penalties, we got under the referee's skin and the game changed," Muir said.

He said the team had known the Brumbies would be tough opponents and at halftime he had thought his players had performed well.

But the second half was completely different.

"Discipline cost us and there's no excuse," Muir said.

"But it's not a train smash for us. We like to win and we know how to play."

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