A year after starting his Brumbies career as the lightning-quick skinny kid, Cox has added six kilograms to his frame in a bid to prove he can match it with the biggest and most powerful wingers in Super Rugby.

The Brumbies challenged a slight Cox to bulk up in the off-season.

Speed has never been a problem for the former Australian football player. But running into players who were, at times, 30 kilograms heavier was the biggest hurdle for the 24-year-old.

To combat that, Cox has been eating up to six meals a day and training harder than ever.

He arrived at the Brumbies weighing just 85 kilograms and was capable of running 10 metres a second.

A year later Cox can still run at that rate but now tips the scales at 91 kilograms and is aiming to add two kilograms in the coming months.

It might seem like an extreme transformation.

But Cox admits he needed to change his body to ensure he wouldn't be used as a speed bump when he gets his Super Rugby opportunity.

''When I came down last year my rugby knowledge wasn't up to scratch and in terms of physicality I've put on six kilos and kept my speed,'' Cox said.

''My goal is to get a start for the Brumbies; I just want a crack. I felt underweight last year … with physicality and aggression it's hard when you're up against a 100-kilo winger, so things are easier now.

''I've got the confidence to get out there and put my body on the line.

''You've got to do a lot of eating and a lot of hard work. We get skinfolds measured so you can't just put on bad fat … I struggle to hold weight so you're looking at five to six meals a day and I'm not a big eater.''

His hard work off the field is reaping the rewards at training.

With Henry Speight, Joseph Tomane, Andrew Smith and Clyde Rathbone being eased back after injuries, Cox has taken his opportunity to stand tall.

He got limited opportunities to impress in his first year at the Brumbies.

After playing in the pre-season trial matches, he couldn't force his way into the regular Super Rugby rotation.

But his blistering pace was on display in a midweek tour match against Wales when he tore through some broken defence and left international players grasping for air.

His goal now is to show coach Jake White he can do that every week.

''Coxy is a totally different beast,'' Brumbies backs coach Stephen Larkham said.

''His communication and understanding of rugby has gone through the roof; he's one of our best trainers.

''He's got a bit more aggression to his game now. There's going to be a lot of competition in the wing position and Coxy has the jump on a lot of guys who are coming back from injuries. ''