The 22-year-old might have missed a regulation penalty less than 10 minutes earlier at GIO Stadium on Saturday, but he stepped up to make an even harder kick after the siren.

About 40m out, Hansen's kick never looked like missing to lift the Brumbies to a 22-20 win and ensure they remain undefeated this Super Rugby AU season.

Allalatoa had full trust in the bench player taking the vital kick, with the Brumbies reeling in a six-point deficit with six minutes to play.

"We continued to play our footy and then the penalty came and he just pointed out the sticks," the star prop said.

"As a player he's come a long way this year. For him to have the confidence there to step up and win the game says a lot about himself."

Brumbies coach Dan McKellar said he was proud that the five-gamer backed himself in.

"He's (Hansen) a Canberra boy who's been supporting the Brumbies since he was a toddler," McKellar said.

"For him to step up with confidence and kick a clutch penalty goal was brilliant so really proud of him.

"He's not going to get rattled by mistakes. He's a kid who will back his skill and ability.

"He'll make a mistake or two here and there, that's him as a footballer, but he backs himself. The pros far outweigh the cons with him."

The result lifts the Brumbies a game-and-a-half clear on top of the ladder, with the Reds left shattered about blowing an opportunity to win their first game in Canberra since 2014.

Australian Associated Press