The scary prospect of being exposed in front of teammates and 80,000 fervent Irish fans at Croke Park is steeling Digby Ioane for the greatest challenge of his rugby career.

Set for just his second Test start at outside centre, Ioane is anxiously aware that Australia's grand slam hopes rest heavily on his ability to contain Ireland's game-breaking wizard Brian O'Driscoll on Sunday.

"It's the biggest test of my life. Everyone knows he's the best centre in the world," Ioane said.

"I'm nervous but, at the same time, I'm excited. You don't get many opportunities like this to test yourself to see where you're at, so it will be awesome.

"I'm just following my older brother's advice. He always says never let your opposite score over you.

"That's the worst thing that could happen, letting him get past me and scoring a try."

Ioane, 24, has good reason for feeling on edge.

O'Driscoll - named Six Nations player of the year this season after leading Ireland to their first grand slam since 1948 - is the highest-scoring centre in international rugby history with 36 Test tries.

The British and Irish Lions captain is also Ireland's greatest-ever tryscorer and will be inspired to deliver an extra special performance in his 100th Test - and the Six nations champions' first of their autumn campaign.

Ioane can't find fault in O'Driscoll's game.

"I was watching videos of him last night, to be honest, and there's nothing wrong with him," Ioane said.

"He's probably the first guy I've watched play and there's nothing wrong - no missed tackles and he always gets over the line.

"And he's old and he's still going, still a gun. He's so experienced."

Ioane is banking on the defensive support of his teammates, particularly wingers Peter Hynes and Drew Mitchell and inside centre partner Quade Cooper, and Wallabies coach Robbie Deans agrees it will take a group effort to stop O'Driscoll.

"If they talk to me, I'm sweet," Ioane said. "But if there's no talk out there, I get a bit lost.

"I've just got this thing: I don't want my opposite scoring a try."

O'Driscoll ran amok the last time the two sides met in Dublin three years ago when Ireland stormed to their biggest-ever win over Australia, a 21-6 triumph in driving rain at Lansdowne Road.

Rain is again on the cards but, having initiated Ioane's move from the wing to the centres during the Super 14 season, Deans has full faith in the five-Test rookie.

"It's not so much a head-on contest. They don't always defend each other or attack against each other," Deans said.

"But obviously there will be parallels made. It's more about how the group thrives and Digby has made that transition well off the back of a full Super rugby season."

O'Driscoll, 30, also appreciates the danger the explosive Ioane poses to Ireland's backline defence.

"He's an extremely powerful runner and a great ball carrier, so he's very much a power athlete," he said.

"But I'm sure he can mix his game up, so I'm sure as the week goes on we'll have a look at him in a little bit more detail."

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