Rocky Elsom faces his moment of truth on Sunday when he must shove friendships aside and lead Australia to a pivotal grand slam victory over rampant Ireland at Croke Park.

Worshipped in Dublin for his European Cup heroics with Leinster earlier this year, Elsom is looking to return to his destructive best when he goes head-to-head with a host of former teammates, including Ireland's superstar captain Brian O'Driscoll.

Wallabies coach Robbie Deans has challenged his inspirational skipper to step up and be the difference in what shapes as a desperately tight Test between the world's third and fourth-ranked teams.

"He hasn't had a lot of carries of late," Deans said.

"Everyone has things they like to do, but not everyone can do the things they like to do all the time.

"They've got to do some of the things they don't like to do because they normally are the things that are the point of difference.

"But obviously he is an effective ball-carrier and we do look to involve him where we can.

"I've no doubt the Irish will be looking for him as well and will be keen to double-team him. We might use him as a decoy, who knows?"

Elsom was at his storming best during his Leinster stint, bagging a swag of man-of-the-match awards and crowning his stay with the European player of the year gong.

His devastating running game terrorised rival defences, but the big flanker admits it's been difficult to transfer that form to the Test arena.

"It's a different team, so it's a different style," Elsom said.

"With Leinster, you'd do like about 15 or 20 carries a game, where it's probably around three or four here (with the Wallabies). It's just a bit different.

"You always want to play better, but you can't let that dominate your thoughts.

"You have a role in your team and you've got to make sure you're doing that first."

His chief role at Croke Park will be nullifying Ireland's dynamite back row.

"It's far and away the best back row in Europe," Elsom said.

"Last year they really dominated and were a big reason why they dominated the Six Nations.

"Jamie Heaslip is a big hitter, good ball carrier and very strong on the ball.

"David Wallace is all those again, he's the opensider, and you'd say Steve Ferris is pretty similar.

"They're all pretty complete players, but just have slightly different dimensions and they play well a lot."

Sunday marks exactly one year since Ireland last lost a Test - against the All Blacks at Croke Park - and Elsom expects the European champions to be a step up in class to England, who crumbled in the second half last week at Twickenham.

"They've got a lot more strike weapons," Elsom said.

Highlighting the strength of the Irish is Paddy Wallace's inclusion at inside centre ahead of British and Irish Lions star Gordon D'Arcy.

"They must have a bit of talent in the squad to keep D'Arcy out of the 22 altogether," Elsom said.

The five-eighth duel between Australian playmaker Matt Giteau and Ronan O'Gara and the outside centre battle between O'Driscoll, in his 100th Test, and the Wallabies's five-Test rookie Digby Ioane could well decide the outcome.

Even Elsom is excited about the midfield match-up.

"In a lot of ways they're pretty similar. Brian's made a career of doing erratic things really well and Digby's probably the same, and both very strong," he said.

"That will serve them both well. It will be good to see them go."

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