Australia v Ireland: Invariably at the cutting edge of international rugby coaching, the Wallabies have always drawn admiring glances from around the world, not least for the inventiveness of their back play.

Eddie O'Sullivan is among their admirers, and nothing about their two highly opportunistic and handsome wins over England has dimmed his enthusiasm.

O'Sullivan has been particularly impressed by the accuracy and potency of the Wallabies' back line, which he describes as a different animal from their All Blacks' counterparts, insofar as the latter use mainly their power and pace to create line breaks and overlaps.

"The Wallabies are a different proposition altogether. I think they have a similar philosophy to ourselves. They like to run a lot of set plays and isolate defenders and pick holes in the gain line, rather than force their way through them. They've always had that headset as a back line, and it's an aspect of rugby I've always admired: Wallabies back play. I've always followed that philosophy myself as a coach."

The two wins over England highlighted their experience and accuracy of execution, which by extension alleviated some of the pressure on a pack that is very much a work in progress.

Hence, O'Sullivan anticipates the ball in play for long spells next Saturday, with plenty of phases and passes, in a fluid, open game of rugby.

"Strangely enough, if the weather is good then I think defence is going to win the game actually. To be fair to both sides, and I'm not trying to blow our own trumpet here, I think we can play some pretty good rugby in the conditions. We've got a good back line on the pitch, and a good pack as well to win some ball.

"I think we have a similar headset to Australia at the moment. Both sides will be trying to run the football, so I think it might boil down to which defends the best over the 80 minutes."

The one change - Geordan Murphy's replacement at full-back by Girvan Dempsey for the latter's first start since the second Test in Japan last summer - might be seen to detract from Ireland's running game.

Ironically, Dempsey has had probably his best season yet with Leinster, but has been confined to five appearances out of eight from the bench, only one of which, a 14-minute stint on the wing in the Triple Crown-clinching win, amounted to much more than a cameo.

O'Sullivan was reluctant to go into detail about Murphy omission.

"I don't think he's on top of his game at the moment, and he'd be the first to admit that himself. I said coming on the tour we would try and pick a team in each week to win a game. It's another tough one on Saturday and we're putting our best foot forward," said the coach, highlighting what after two bruising Tests is an unusually clean bill of health.

It's disappointing that Murphy's creative skills haven't been brought to the fore and that such a talented line-breaker has looked short of his best. Murphy is joined on the bench by Jeremy Staunton, to the exclusion of Denis Hickie, though in retaining the option of Murphy as cover for Ronan O'Gara, O'Sullivan doesn't exactly offer a ringing endorsement of the Wasps outhalf.

"He's had a couple of weeks to get into our system, he's more comfortable than he was so he deserves a run on the bench, and we'll see how he goes," added O'Sullivan. "I'm not making any definitives about substitutions or anything about 10. But he's there and we'll see how it goes."

The net result is that 14 players will have started all three Tests, and seven of the squad have had no involvement in any of them. In maintaining fatigue should not be a factor given the way the squad have been managed on this tour, O'Sullivan revealed that John Hayes had likened the first Test against the All Blacks to a foot race, because of the high tempo on a dry night in the superbly manicured Waikato Stadium, whereas the second Test, in the rain-sodden Eden Park, was more like a boxing match.

O'Sullivan confirmed the impression that the Irish scrum responded to their difficulties in the first Test by emulating the All Blacks in engaging late, from the same height and with the same momentum, before they were wheeled on their own put-in, and not necessarily legally.

"I don't think we can allow Australia do that," said O'Sullivan. "I'm quite happy that we'll be okay against Australia. It's not an area that we struggled in last autumn against them, but I'm not taking anything for granted either. I'd be surprised, put it this way, if we have issues in the scrum on Saturday."

Speculation is widespread in the local media that O'Gara's defence will be targeted by the Wallabies.

"It's a bit like a dump-truck hitting a bike - it's a bad match-up," explained O'Sullivan. "We're not going to put another 30 pounds on Ronan. It's not that he's not trying to tackle, it's just a mis-match, and you've got to try and work round that. He keeps working on his defence and occasionally he gets caught, and we've got to be more aware of it."

The hoary old chestnut of impact replacements reared its head, O'Sullivan disputing the true meaning of the term. Taking the prime example of a big, ball-carrying replacement, he said, "I don't know if we have anyone of that category on the bench ahead of the guys on the pitch."

"Substitutions have to be for a good reason, either an injury or a player isn't playing well or someone who is going to change the pattern of the game, and that's my take on it.

"It's kind of an easy term to throw out impact replacements as a cure-all-ills. When you analyse it, it's a little more complex."

He conceded the All Blacks' replacements had a big impact on outcomes, especially in the first Test, but countered: "Because of the depth in their playing pool there's not a ton of difference between one guy or another. They're all big, athletic players.

"No matter what Irish team we pick, it's hard to get 22 guys who are huge athletes and impact replacements who run over tired people. We don't have a lot of those in Irish rugby and our impact replacements are often tactical replacements."

Ireland (v Australia)

15 Girvan Dempsey (Leinster)

14 Shane Horgan (Leinster)

13 Brian O'Driscoll (Leinster, c)

12 Gordon D'Arcy (Leinster)

11 Andrew Trimble (Ulster)

10 Ronan O'Gara (Munster)

9 Peter Stringer (Munster)

1 Marcus Horan (Munster)

2 Jerry Flannery (Munster)

3 John Hayes (Munster)

4 Donncha O'Callaghan (Munster)

5 Paul O'Connell (Munster)

6 Neil Best (Ulster)

7 David Wallace (Munster)

8 Denis Leamy (Munster)

Replacements: Bryan Young (Ulster), Rory Best (Ulster), Mick O'Driscoll (Munster), Keith Gleeson (Leinster), Isaac Boss (Ulster), Jeremy Staunton (Wasps), Geordan Murphy (Leicester)