Ireland coach Eddie O'Sullivan knows D'Arcy and his midfield partner Brian O'Driscoll will get fewer opportunities to make attacking breaks this weekend than they did against the Springboks last Saturday.
O'Sullivan said: "Australia don't defend like South Africa. They play with a softer line so it won't be as easy. You get a lot more space but they hedge their bets a bit more. South Africa missed some tackles because our running lines were good and that made it very difficult for them to get good hits on us.
"Their blitz defence is either a complete success or a complete failure - there isn't much in between. It is a high risk strategy against the likes of O'Driscoll and D'Arcy, who can beat anyone in a phone booth. It will be a different challenge to break Australia down.
"You have to create space against Australia, whereas against South Africa the spaces are there, the difficulty is getting into them before you get hit."
One man who is relishing the chance to test himself against the Wallabies is Leinster winger Denis Hickie. The 30-year-old Dubliner, who is still Ireland's second top try-scorer, has not played for Ireland since March 2005 - last game was the RBS 6 Nations clash with Wales in Cardiff.
He was an unused replacement in last June's two Tests against the All Blacks and failed to make the matchday 22 against Australia in Perth.
Hickie has played twice previously against the Aussies, in the 18-9 win at Lansdowne Road in 2002 and the 17-16 defeat in Melbourne at the following year's World Cup. He will have bad memories of the latter game - he ruptured his Achilles tendon late in the first half, an injury which ended his World Cup campaign.
David Wallace, Malcolm O'Kelly and Peter Stringer warm-up for the session at St. Gerard's. If O'Kelly is called on, he will be making his 82nd appearance for Ireland this Sunday. Just like Hickie, the Leinster lock has bad memories of his last outing against Australia.
During the first half of last November's 30-14 loss to the Aussies, O'Kelly was knocked unconscious following a double tackle by Lote Tuqiri and Nathan Sharpe. Should he be sprung from the bench, the maths master will be earning his eighth cap against Australia in ten seasons.
Ulster's New Zealand-born scrum half Isaac Boss is bracing himself for his first start for Ireland this weekend. Boss, 26, earned his second cap as a replacement against the Aussies last June and Eddie O'Sullivan has no fears about putting him in.
The Corkman said: "Isaac's a different player to Peter (Stringer). He's more robust in some ways, he's more aggressive around the fringes. He likes to take on the back row off scrums, the pillar defenders at rucks. He's the kind of guy who can create problems in that area.
"It took him a while to settle in but this year he's been very effective for Ulster. On form, he's fought his way into the side."
Eddie O'Sullivan, pictured alongside his assistant coach Niall O'Donovan, will want to improve his record against Australia this weekend. Since the 18-9 victory at Lansdowne Road in 2002, O'Sullivan's charges have lost four successive games to the Wallabies - losing by 20 points-plus in three of those fixtures.
A leaping Donncha O'Callaghan leads his team-mates at Wednesday's training session. Adding a consistent streak to his game, the Munster lock is beginning to bed himself into the Irish second row - Sunday will mark his fifth straight start for Ireland, and all of those caps have come against Tri-Nations opposition. His one and only try to date was against France in last season's RBS 6 Nations.
Denis Hickie, still with pace to burn, has scored four tries in seven Magners League outings for Leinster this season and deserves his return to senior international duty. His wing battle with Clyde Rathbone should be an intriguing one on Sunday.
Eddie O'Sullivan said of the Leinster stalwart's recall: "Denis has been unlucky with injuries. He broke his leg last year and missed the start of the season. Unfortunately for him, Andrew (Trimble) burst onto the scene.
"He was frustrated on the summer tour and I told him to keep plugging away and he has done. And now the opportunity has arisen probably sooner than it might have. But he knows how it works."
Malcolm O'Kelly, squeezed out of Sunday's starting XV by Donncha O'Callaghan, first played against Australia in Perth in June 1999. Despite tries from Peter Clohessy, Justin Bishop and Kevin Maggs, the Warren Gatland-coached Irish went down 32-26 to their hosts back then. The only other surviving members from that Perth squad are Brian O'Driscoll and Girvan Dempsey.
**All photos by Donall Farmer of Inpho Photography**
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