Mogg could be thrust into the most intense arena of his career if the Wallabies call on him from the bench in the series-deciding Test against the British and Irish Lions on Saturday night.

Just a week ago Mogg sat on the bench waiting for a chance to make his debut, but coach Robbie Deans shelved plans to inject the ACT Brumbies flyer with the result hanging in the balance.

Brumbies teammate Nic White spent three Tests on the Wallabies bench as a back-up halfback last year, but never got on the field.

But Mogg - who will sit on the bench again at ANZ Stadium in the third Test - is determined to prove he can be a super-sub, not just a cheerleader.

''I've spoken to Robbie during the week and he told me to, 'do what you normally do, because you're good at it','' Mogg said.

''Robbie got me to warm up last week, but then we scored and the game changed.

''I don't have to change too much, just take opportunities when they come and find my groove in the team. I think in the last two or three weeks I've learnt how to deal with pressure and get the team on the front foot.''

Mogg is just one of two back-line reserves for the Wallabies' biggest game since the 2003 World Cup final.

Melbourne's Nick Phipps is the back-up No.9 while it's likely Mogg will be called on if there's an injury in any other position in the back line.

Mogg has established himself as the Brumbies' first-choice fullback after making his Super Rugby debut last year.

He was left out of the initial Wallabies squad for the series against the Lions, but was called in when Pat McCabe and Digby Ioane were ruled out with injury.

''I definitely feel more comfortable this week, I really hope I'm involved on the field this week and do what I can for the team,'' Mogg said.