After fighting back from a 13-point deficit in the second half, a 54-metre drop goal in the dying minutes sunk the Brumbies to  27-21 loss, their fourth of the season.

The loss was even harder to swallow following a host of controversial refereeing decisions.

Winger Henry Speight had a try disallowed early in the first half because it was ruled there was an obstruction, a Brumbies penalty was overturned for a seemingly innocuous incident when Nic White pushed Heinrich Brussow on the face and Scott Fardy was sent to the sin bin.

Referee Marius van der Westhuizen was in charge of just his third Super Rugby game and Brumbies skipper Ben Mowen had a running battle with him for the entire game.

The Brumbies were their own worst enemy, putting themselves in poor positions and giving away silly penalties to allow the Cheetahs to keep extending their lead.

The Brumbies were perplexed with some rulings, but admitted they "shot ourselves in the foot" and failed to take their chances to win the game.

They missed a chance to stretch their lead in the Australian conference after the Western Force lost to the Cape Town Stormers and the NSW Waratahs will play the Johannesburg Lions on Sunday.

Perhaps the only positive out of the game was the Brumbies' securing a crucial losing bonus point which could be pivotal in the tight Australian conference battle.

"When you travel away, you can't leave effort areas and decisions in other people's hands, you have to be good enough to take those opportunities yourself and we definitely weren't tonight," Mowen said.

"The attitude was pretty good, it was just execution that cost us."

Brumbies scrumhalf White regretted giving away a penalty when the Brumbies were peppering the Cheetahs line.

The Brumbies were awarded a penalty for cynical breakdown play by the Cheetahs one metre from their line.

But Brussow killed the advantage, grabbed the ball and booted it away after the referee blew the whistle. Brussow was sent to the sin bin for the same incident in the second half.

White tried to charge down Brussow's first-half kick, and pushed the flanker in the face and a fracas broke out.

Van der Westhuizen then reversed the penalty and awarded the ball to the Cheetahs for a soft incident.

White said he reacted out of frustration because teams kill the ball when a penalty advantage is given.

"I wanted to play the advantage because it's a free shot, but when they infringe again and then take the ball and pretend to kick it away ... I was just frustrated I couldn't get the ball," White said.

"Teams are doing it now and it seems they're allowed to infringe at no risk when there's an advantage. It's hard to get an advantage. I certainly didn't hit him in the head, I was frustrated and it's something I regret now."

The Cheetahs struck twice in 12 minutes after half-time to turn a deficit into a 10-point lead with Willie le Roux and Johan Goosen scoring tries.

Goosen finished the game with a 22-point haul, booting four penalties and a long-range drop goal to put the dagger through the Brumbies in the dying minutes.

His try was equally as impressive, turning from playmaker to winger to leap above Robbie Coleman to steal the ball and score in the corner.

The Brumbies have to regroup for a daunting task against the Pretoria Bulls at Loftus Versfeld next week, one of Super Rugby's toughest venues for visiting teams.

"They hassled us and once you lose that momentum you're chasing the game. The Cheetahs hussled us in defence, there are some things we can look at," Mowen said.

"The last time we were [in Pretoria] we had a really good win. It doesn't get easier on tour, but if you want to be there at the end you have to be able to do it so we're looking forward to that challenge."

The Brumbies appeared to strike first with a superb set play for returning winger Henry Speight.

His Fijian teammate Tevita Kuridrani ran a decoy, but the officals deemed there was an obstruction and the try was disallowed.

Brumbies skipper Mowen pleaded with referee van der Westhuizen to make the same calls for both sides, but the Brumbies struggled to get any momentum in the opening exchanges.

Flying ACT winger Robbie Coleman scored the first try of the match when White grubbered through to get behind the Cheetahs' defence, with Coleman winning the race to the ball and the line.

Superstar Cheetahs back WIllie le Roux put his team back in front just after the break with a well-worked move from a lineout.

The Cheetahs slipped through a gap when they caught the Brumbies defence napping and le Roux flew down the sideline to score the second try of the game and put the home side back in front.

The Cheetahs extended their lead just minutes later when Goosen scored. When he converted from the sideline, the Cheetahs were in front  by 10 points.

All of a sudden everything was going the Cheetahs' way. They won a scrum penalty against the feed and then a mongrel punt for touch somehow found the line between two Brumbies players.

The tide turned came when Heinrich Brussow was sent to the sin bin with eight minutes remaining.

From the attacking lineout, the Brumbies set a rolling maul and Stephen Moore crossed for a try to cut the margin to three points.

But Goosen nailed a 54 metre drop goal to give the struggling Cheetahs a morale boosting win in an otherwise disappointing season.

AT A GLANCE

FREE STATE CHEETAHS 27 (Willie le Roux, Johan Goosen tries; Johan Goosen 4 penalties, conversion, drop goal) bt ACT BRUMBIES 21 (Robbie Coleman, Stephen Moore tries; Nic White 3 penalties, conversion) at Bloemfontein on Sunday morning. Referee: Marius van der Westhuizen.