If Ireland was already feeling some trepidation about starting their World Cup campaign against a former coach after losing four straight warm-up matches, then the date and choice of opponent have done little to help.

The injury-hit and morale-battered Irish will play the United States at New Plymouth on Sunday - the 10th anniversary of the 9/11 attacks, the worst act of terrorism on American soil.

Ireland hooker Rory Best says he is ready to play against a group of players, led by former Irish coach Eddie O'Sullivan, whose motivation to perform with distinction for their country will rarely be equalled.

"September 11 will be a momentous day for them. They'll be charged," Best said. "The first 10 minutes will reflect that and we must make sure that, at worst, we're able to match their physical intensity."

Making it harder, prop Cian Healy (eye socket) is unlikely to play while centres Brian O'Driscoll (shoulder) and Gordon D'Arcy (calf) plus flank Sean O'Brien (knee) and fullback Rob Kearney (groin) have been battling injuries and received only limited match-time recently.

O'Sullivan coached Ireland when they performed so disastrously at the 2007 tournament, when they struggled to beat Georgia and Namibia before exiting at the pool stage - the sixth straight time the had failed to progress beyond the quarterfinals at the World Cup.

That signaled the end of his reign at Ireland and he now returns in charge of an American Eagles outfit that has won just two of 15 matches at the World Cup.

"He's probably got a lot of inside knowledge on the way our guys like to play and I'm sure he'll be tipping his team off to our strengths and weaknesses, so we've got to do our homework on those guys and give them the full respect that they deserve," Ireland back Geordan Murphy said. "Eddie's done a tremendous job with Ireland over the years, but it's not really a massive factor for us. We just have to play the opposition."

Ireland possesses the oldest squad at the tournament, the average age being more than 29 years. But only 13 current squad members were in France four years ago, indicating that playing maturity and World Cup experience don't necessarily go hand in hand.

It is probably an advantage for those 17 other players to have missed Ireland's diabolical performance in in 2007, however they all played at least some part in the team's four straight warm-up losses for this event: Twice to France and once each to England and Scotland.

"During the warm-up games we were mentally off-pitch. Since we've arrived here I've noticed a difference in attitude among the players," flyhalf Ronan O'Gara said. "Maybe we viewed the warm-up games as trials while other countries saw them as full-on Test matches.

"There's no panic in the camp. We're not denying that we wanted to win those games, but at this level you have to be at fever pitch. We weren't and it's important we are during the World Cup. That should bring out the best in us," he said.

For senior players such as O'Driscoll, O'Gara, Murphy and lock Paul O'Connell, the tournament represents the final chance for them to restore Ireland's reputation. The core of the team that won the 2009 Six Nations Grand Slam remains, but O'Gara is reluctant to make any predictions.

"Until you perform at a World Cup, you shouldn't talk about it because you haven't done it," he said. "With Ireland, we haven't earned that respect at world level. It's up to us to try and earn it."

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