Ireland coach Eddie O'Sullivan has hinted that he may rest key players and will take no selection risks heading into Saturday's eagerly-anticipated pool game against Australia.
Ireland sealed a place in the last eight with a heart-stopping 16-15 victory over Argentina in Adelaide and whom they meet depends on the result of this weekend's showdown at a sold-out Telstra Dome.
The winners will top Pool A and avoid the daunting prospect of facing France, but that is only of secondary importance to O'Sullivan.
"We have a minimum of two games left in Rugby World Cup and the most important game to win is the second one," he said. "If we win on Saturday and lose the following one we are going home. If we lose on Saturday and win the following week we stay for the duration.
"What we have to do this weekend is go in and give it our best shot, try and get past Australia and make a different landscape for ourselves going into the quarter-finals.
"But at the end of the day, you wouldn't want to risk anyone because the quarter-final is the game that makes the difference on our progression.
"That doesn't mean we are taking our foot off the pedal for Saturday, it doesn't mean we won't be hitting any harder or trying any less, but it might colour our thinking on selection.
"It might weigh in terms of selection - if a player is borderline you might rest him to make sure he is fit for the quarter-final.
"That is the only thing that might factor into it."
Ireland's chief injury concerns currently involve Victor Costello and Kevin Maggs, who both picked up knocks against the physical Argentines.
They are not alone in suffering bumps and bruises, which is why O'Sullivan broke from normal Irish protocol in choosing to name his side on Thursday.
"There are a lot of sore bodies and guys that are carrying knocks and bruises," he said. "The guys of concern are Victor Costello, who took a knock in his thigh, and Kevin Maggs who went over on an ankle but we are expecting both to be fit and well by the weekend."
Into the equation comes David Wallace, who arrived in Melbourne today as replacement for the unfortunate Alan Quinlan, whose impressive World Cup campaign was ended by a dislocated shoulder.
He joined in training immediately after arriving and then went to bed in a bid to counter the jet-lag.
The fly-half debate has, predictably, reopened again with David Humphries vying for the starting role with long-time rival Ronan O'Gara.
Humphries got the nod for the Argentina game, as he did against Romania, but O'Sullivan insisted it was back to a level playing field heading into this coming weekend.
"It's another typical selection. We want to put the guy on the pitch who is going to do the best job for us on Saturday," he said. "Sometimes the job description changes, but with the two players we have it is the toss of a coin. It's often down to who is looking the best or who is showing the best type of form.
"I know you would all like to know, and so would a lot of other people, including myself - these decisions take a lot of time and a lot of weighing up.
"Every decision we make we leave to the last minute when you have all the data in front of you and you feel you are making the right decision.
"The outside half position is up for discussion as it always is and hopefully always will be."
Who wears the number 10 shirt is traditionally Ireland's major selection quandry, while O'Sullivan's Australian counterpart Eddie Jones is trying to squeeze both Mat Rogers and Chris Latham into the fullback jersey; Lote Tuqiri, Wendell Sailor and Joe Roff into the two wing berths while Matt Burke and Stirling Mortlock are vying for the outside centre role.
Jones described it as the ideal problem, but O'Sullivan is unfazed - and even had a little dig at how the draw has fallen for the Wallabies.
"They can only put 15 men on the field, and we can put on 15 as well," he said. "The key for us is that if we get a full deck to play from we can put a good team on the field and can play with anybody.
"It's panned out well for Australia, they got the tricky one out of the way against Argentina then have had two pretty straight forward games.
"And now their final one, with a full seven days' rest and players being held back the previous two weeks, they are going fully loaded into this game.
"Being the host nation there was always a chance things would fall their way in that respect."