Beauden Barrett has slotted a field goal after the fulltime siren for the Blues to steal a famous Super Rugby Pacific victory from the Brumbies in Canberra.

The Blues' 21-19 win - a club record 12th straight victory - moved them further ahead on top of the ladder and all but relegated the Brumbies to third place with one round to play.

The Brumbies went ahead by one with Billy Pollard's try and Noah Lolesio's clutch conversion with 70 seconds to play.

The Brumbies won the ball from the restart but lost possession and then watched as the visitors worked towards the posts, winning a penalty despite protests from the hosts before All Blacks playmaker Barrett used the advantage to slot the winner.

The Brumbies were furious at a penalty count 16-5 in the Blues' favour and at one point had made 95 tackles to the Blues' 38.

The hosts had shot out of the blocks though and led 7-0 after Pete Samu found a patch of grass to plant the ball in the second minute.

But it was all the Blues after that, the Auckland outfit applying immense pressure as they threatened to reply.

But it remained that way for almost 40 minutes, Roger Tuivasa-Sheck one of three would-be Blues scorers held up over the line.

Kurt Eklund thought he'd broken the drought but had his try disallowed for a knock-on, that decision triggering a yellow card for Brumbies hooker Folau Fainga'a for repeated infringements.

Darcy Swain soon followed to leave the Brumbies with just 13 players, but again they held firm until Barrett crossed for a try off a scrum after the halftime siren.

Brumbies halfback Nic White turned the tide after the break with a sharp intercept, running 80 metres before Fainga'a scored soon after from a maul to put the hosts back in front.

Blues winger Caleb Clarke limped off with a hamstring injury and the usually-reliable Blues goalkicker Stephen Perofeta then missed a penalty to go with an earlier failed conversion.

But they kept coming, Karl Tu'inukuafe coming up with the ball in traffic close to the line and popping over to put the Blues back in front with 14 minutes to play.

Perofeta found his range with a penalty to make it a six-point game inside the final five minutes.

Pollard scored his late try off a trademark Brumbies lineout and maul and Lolesio snuck his conversion inside the right post to put them up by one with 70 seconds to play before the Blues pulled off their great escape.