Anticipating plenty of trench warfare from the Argentinians in Sunday's pivotal Pool A tie, Eddie O'Sullivan will send out probably the biggest Irish pack to ever take to a rugby field. If it's grunt and grind Los Pumas want, it's grunt and grind they're going to get, writes Gerry Thornley in Adelaide

With Reggie Corrigan and John Hayes back in harness for the first time in a starting Irish front-row since February in Rome a dozen tests ago, O'Sullivan has gone for a big back row in Simon Easterby, Alan Quinlan and Victor Costello, whose return along with David Humphreys constitutes the only two changes from the win over Namibia.

In sacrificing the squad's one true openside, Keith Gleeson, even from the 22, to accommodate Quinlan, the Irish coach calls it a horses-for-courses selection.

At 6ft 2in, Corrigan is the second shortest member of the pack, where the average weight is 17 stone 2lbs.

In expectation of "a pretty physical, close-quarter encounter" O'Sullivan reasoned: "We've gone for some physicality and bulk in the back row, to match up there. It's something we always had in mind to do when we played Argentina. So it's a reflection on the type of team we're playing and the type of team we're going to play."

O'Sullivan admitted that the injured Anthony Foley was "in that genre of player" and should be back in training by Friday. It would have been interesting to see what the back-row combination would have been had Foley been available.

Not too dissimilar perhaps, with Easterby (statistically the best tackler and hardest worker in the squad) seemingly having long since been earmarked for this game, given the Pumas' penchant for pummelling away around the fringes.

O'Sullivan admitted he'd been thinking of this type of line-up "a long way back to be honest with you. Pretty much since we played them in November and we've watched how they've played since."

Combined with Costello's ball-carrying and Quinlan's innate aggression and physicality, Ireland are well equipped for fringe warfare anyway.

"The guy who feels hard done by, and rightly so, would be Eric Miller, who had a super game last week," commented O'Sullivan. "It's a tight call in these situations, which is a reflection on the type of player we have."

At least Miller can console himself with being on the bench. Not so Gleeson, and one can't imagine him being thrilled by his omission.

For all of last season's record-winning run it seemed that the squad's most effective man at recycling the ball at the breakdown was one of the first names on the teamsheet, starting in all but the Fijian match during a 14-game sequence until the defeat in Perth last June.

O'Sullivan made it abundantly clear to players and media alike that this was a horses-for-courses selection which "is nothing against Keith Gleeson" and is likely to change the following week against Australia.

Even so the Leinster flanker does seem to have fallen out of favour a little. He was given leave of absence from Tonga and Samoa, thus in Ireland's eight matches since Perth, Gleeson started in two of them.

As a result, this team does not seem as designed to play the wide-wide, quick-rucking game that was unveiled against England in the Grand Slam decider, especially bearing in mind that the Pumas have never looked more vulnerable than when Australia attacked them wide out and then quickly switched play back across field in the tournament opener.

It is in some respects a counterfoil to the Argentinians, though it certainly can hurt them, not least in the lineouts. With Malcolm O'Kelly, Paul O'Connell, Easterby and Quinlan to choose from, Ireland have sufficient targets both to keep Argentina guessing and to wreak the same kind of damage on the Argentinian lineout which the Wallabies did in the opener.

"I think the Pumas are a team who are very clear in how they want to play the game," said O'Sullivan.

"There is a Puma style of rugby that everyone recognises. And they know that if they execute well in that style, they can probably beat any team in the world. I don't think they'll be taking too much stock of Ireland in that respect. They'll play their game, they'll be very aggressive at scrum time, very aggressive at maul time, and they'll be very aggressive in the tackle at ruck time and maul time. It'll be a bruiser, and it'll be hand to hand combat, and it won't be for the faint-hearted."

There are six survivors from the line-up four years ago which lost to Argentina in the quarter-final play-off in Lens: Brian O'Driscoll, Kevin Maggs, Humphreys, Corrigan, Keith Wood and O'Kelly.

"I knew this would come up somehow," said O'Sullivan in reference to that match. "I find it strange we're still dealing with Lens. It's four years ago. I wasn't there, and I'm not abdicating any responsibility for that, but a lot of the team weren't there. What I'm looking back to is November when we, and I include you, all said that this would be a great test for Ireland and will throw down a marker for the World Cup.

"We went out and performed very well in pretty bad conditions, which didn't necessarily suit us, and won the game. It was a tight game, we didn't run away with it, but it was a good solid performance and I think that's what I'm looking back on. We know we need a performance even better than that. It's going to be a very tight game. For that reason, Lens isn't really in there for me or the players."

O'Sullivan admits he's afraid to look at the weather forecast after "a typhoon in Gosford and a monsoon in Sydney, so maybe it's a hurricane this weekend."

On a scorching hot day in Adelaide yesterday, there was further evidence of a palpable shift in mood and intensity this week. Hardly surprising really. Ireland know that if they win on Sunday they are in the quarter-final.

"It's very simple. It's exactly where we wanted to be. We wanted a very clear picture in our mind this week. The goal for the team is very simple - go out, deliver, win, move on - and certainly there is a clarity of thought, a clarity of intent. There's a change of gear and focus, which no matter how much I tried I probably wasn't going to get in the last two weeks.

"So let's bin that now until Sunday and deliver the performance we've been talking about among ourselves all week."

IRELAND: Girvan Dempsey; Shane Horgan, Brian O'Driscoll, Kevin Maggs, Denis Hickie; David Humphreys, Peter Stringer; Reggie COrrigan, Keith Wood (captain), John Hayes, Paul O'Connell, Malcolm O'Kelly, Simon Easterby, Victor Costello, Alan Quinlan. Replacements: Shane Byrne, Marcus Horan, Donnacha O'Callaghan, Eric Miller, Guy Easterby, Ronan O'Gara, John Kelly.