Murphy will be thrown into a brutal forward-pack contest when he makes his starting debut for the Brumbies against the Durban Sharks at Canberra Stadium tomorrow night.

Initiations don't come much tougher than lining up against Sharks and Springboks veteran tighthead prop Jannie du Plessis.

But far from being daunted by the task of leading the Brumbies' scrum against the experienced Sharks pack, Irish-born Australian citizen Murphy wants ''people to accept that I'm not here to mess around''.

''I don't want people second-guessing if I'm good enough or if I'm not to be at this level,'' Murphy said.

''I'm here to play rugby and I'm here to prove myself.

''If it's du Plessis I'm up against, it will have to be him that I take on and I'm happy to do that.

''I wouldn't have it any other way and if I prove myself this weekend then hopefully people will accept I'm not here to mess around.''

Murphy is one of two new faces in the Brumbies' starting XV for the round six clash, with flyhalf Matt Toomua returning from injury.

Christian Lealiifano has moved back to inside centre while Pat McCabe shifts to the wing and Joseph Tomane is on the bench.

The Brumbies expect the Sharks to try to bully them in the battle of the forwards, but coach Jake White said the team was ready to continue its impressive start to the season.

The Brumbies have won three of their four games and sit at the top of the Australian conference.

''The Sharks have 930-odd Super Rugby caps, 10 Springboks and two on their bench … they were spoken as one of the favourites of the competition so it's a big game for us this weekend,'' White said.

''It's just about building on momentum and improving every week when we get out there.

''We've got a different challenge now and we've got to keep improving like we have.'' Murphy's elevation into the starting side has been part of his 10-month mission to establish himself in Australia.

Born in Dublin, Murphy moved to Perth when he was one and lived there for 13 years before moving back to Ireland.

After stints with the Ireland national junior teams and with Exeter in England, Murphy moved to Brisbane last year to try to land a Super Rugby contract. He succeeded when White offered him a deal.

The 24-year-old is the Brumbies' foreign player because the IRB has ruled him ineligible to play for the Wallabies despite holding both Australian and Irish passports.

To be eligible to play for the Wallabies, you have to have lived in Australia for three years or have a parent or grandparent born in the country.

The Brumbies are still fighting to have Murphy classified as an Australian player because he has citizenship after living in Perth for 13 years, but the loosehead prop insists the ongoing battle is not a distraction.

Murphy hopes he can gain a ''cult'' Irish following and forge a successful career at the Brumbies. ''The only difference over here are the accents around me,'' he said. ''Every now and then my [Irish accent] comes out stronger and the boys give it to me, but then I ring home and they say I sound Australian.

''I get a lot of 'the leprechaun' every now and then … Anthony Hegarty and Scott Fardy like to get stuck into me.

''It wouldn't be the worst thing if I could get a cult following and some fans wanted to jump behind an Irish guy, that would be great.''