O'Sullivan - knows his side must perform.

By Gareth Duggan, PA Sport, Melbourne

Ireland coach Eddie O'Sullivan believes his team's Six Nations win over France provides confidence but not certainty ahead of the two countries' World Cup quarter-final on Sunday.

The French have named almost the same pack but a vastly different backline from the one which lost 15-12 in Dublin in March, and O'Sullivan believes it is those changes which present his side with the greatest danger.

"We have had some success against France in recent years," O'Sullivan said of a record which shows Ireland winning three of their last four matches against Les Bleus.

"All it does is confirm we're capable of beating France if we get things right," he said.

"It doesn't mean it's a foregone conclusion, obviously. It's a question of getting our minds around the fact that if we deliver a big performance we can win the game."

The two teams have a familiar look about them for anyone who sat through the tense encounter at Lansdowne Road, but the biggest change is in the French back division.

Left winger Aurelien Rougerie is the only survivor and the development by coach Bernard Laporte of their attacking options has O'Sullivan very wary indeed.

"In the backs it's a different cocktail in terms of trying to defend and attack against them. They seem to have got the balance right now with people in the right places," he said.

"Their centre combination is very strong, they have pace in the back three, and (Frederic) Michalak is always testing the gain line.

"It's a pretty balanced backline in the respect that their strike points are varied. It's a very good backline and it's a better backline than played in Dublin.

"We're going to have to be very diligent and patient in defence to stay with them and if they make a break or get a bust, they usually finish it."

France have been impressive in racking up 204 points in their four pool matches, their only period of discomfort coming in the first half against Japan.

The return of powerful centre Tony Marsh has been crucial, while the halves combination of skipper Fabien Galthie and Michalak has provided invention and consistency.

"They have a rhythm and a pattern to their game that's very structured, but at the same time gives them the latitude to play the style of rugby they know best," said O'Sullivan.

"They have a rhythm to their attack which is quite potent and they have game breakers, so if somebody makes an error or slips off a tackle, you're punished very severely."

Perhaps the biggest issue for Ireland is whether they can lift themselves for a third difficult match in a short space of time.

While France have been essentially untested, O'Sullivan's men have had to dig into their reserves of physical and mental energy to first beat Argentina by one point and then push Australia hard before losing by the same margin.

"I'm convinced we're not battle weary, but we're looking forward to the game and we've got an extra day under our belts where we're off our feet, and I think that makes you battle-hardened," he said.

"Everyone is in the same kind of mind as they were last week. There's a little more pressure in that it's a game we have to win or we're going home, so there's maybe a bit more tension there."

O'Sullivan has made just one unforced change to his line-up from the team which went so close against Australia, recalling Victor Costello at number eight in place of Anthony Foley.

The other alteration is forced, with Munster's John Kelly replacing the injured Denis Hickie on the left wing.

And O'Sullivan is delighted to have a crack second-row unit taking the World Cup by storm.

Ireland's 'O-Team' dismantled the Australian line-out last week, harried the Argentinian set-piece the week before and are swiftly shredding their old "creaky" reputation.

The transformation has been possible largely because, in Paul O'Connell and Malcolm O'Kelly, backed up by Donnacha O'Callaghan, Ireland have dominant jumpers with an impressive reading of the line-out.

"We're fortunate to have some very athletic locks in O'Connell and O'Kelly and O'Callaghan - it seems you have to have an 'O' in your name to play in the second row for Ireland at the moment," joked O'Sullivan.

"Those three guys have worked with guys on the ground like props John Hayes and Reggie Corrigan.

"It's a combination of hard work and good coaching and good players in that area.

"It is an important part of the game and if it functions well, both in attack and defence, it can be a platform for winning the game.

"It was an area of our game that was very creaky a few years ago. I remember in my first Six Nations the line-out didn't flow at all and put us under horrendous pressure.

"We were working off an older system that we had, and it was only when we got to New Zealand after the Six Nations that we had a chance to rebuild our line-out.

"Credit to our forwards and line-outs coach Niall O'Donovan, he has done that extremely well.

"In our last few games we won some crucial line-outs. In the Argentina game, in the second half we were very effective in spoiling their ball or poaching it and we took some very important ball off Australia last week.

"It didn't win us the game but it got us very close to winning the game."

O'Sullivan believes O'Connell, at 6ft 5in and 17 stone, has emerged as the biggest plus of Ireland's second-row development.

The Munsterman will win his 15th cap against France rated by his own coach as one of the finest second row exponents in the game.

"I think he has come through as a world-class second row," said O'Sullivan.

"If you look at his performances he is right up there with any second row in the tournament.

"He has had a tough time with injuries. He had a back operation and he has had a fractured wrist - but he has emerged as one of the players of the tournament.

"He is a very important player for us. His line-out work is superb; his ball carrying ability, his aggression in the tackle - he is a pretty complete footballer."