O'Sullivan: United States coach

The World Cup clash will mark the second time O'Sullivan has faced his former paymasters since his removal as head coach in 2008.

Under his guidance Ireland won three Triple Crowns in four years and climbed to third in the world rankings, though the real prize of a Grand Slam or RBS 6 Nations title always eluded him.

Many of those players who worked beneath him between 2001-08 have spoken highly of him in the build-up to Sunday's showdown at Stadium Taranaki.

Brian O'Driscoll has stated that he has never been given the credit he deserves and knows he will be determined to cause an upset on the 10th anniversary of September 11.

O'Sullivan, however, insists it is business as usual.

"I wouldn't say I have mixed emotions. It's not an emotional feeling," he said.

"It feels a bit strange because I know many of those lads pretty well.

"But it's not about me, it's about the American team. These lads have put in huge effort to make it here to the World Cup.

"In particular the guys who are not professional have made huge sacrifices to come to the World Cup. It's about them.

"The fact we're playing Ireland in the group stage is just the way it's panned out. I have a job to do.

"It's a bit of help knowing what I do about the Irish players and I've been passing that on.

"But we can't get hung up on Ireland, we need to focus on our own performance."

The low point of O'Sullivan's time as Ireland coach was the 2007 World Cup when he presided over their humiliating group exit from the tournament.

Four years ago they had high hopes of reaching the semi-finals, but O'Sullivan is refusing to make any predictions for them in New Zealand.

"I'm not involved with Ireland any more, it's not for me to lay down markers or set the bar for them," he said.

"It wouldn't be right. They have their own objectives and goals. I'm concerned with the Eagles and how well we do."

While the fixture against Ireland is full of personal intrigue, for the USA the World Cup is all about one match.

"Winning the Russia game is the big one for us. We feel like it's within our ability to beat them," said O'Sullivan.

"We played them at the Churchill Cup in 2010 and this year and won those games, though they were nip and tuck affairs.

"They're ranked close to us so we will have to be on our game to win, but we need to target that match.

"Historically for us to win a pool match is very good, we've only had two group victories in the World Cup before.

"We won't roll over dead in the other games though, especially in the first one because you need to make a good start."