Ireland will on Sunday aim to overcome the loss of five key players including fly-half Johnny Sexton to beat Argentina and reach the Rugby World Cup semi-finals for the first time.

Sexton was ruled out of the quarter-final which kicks off at Cardiff's Millennium Stadium at 1300 BST (1200 GMT) after his groin injury flared up again, the IRFU confirmed Saturday.

The 30-year-old -- who went off with the injury in the first-half of the 24-9 victory over France last Sunday -- is expected to be replaced in the starting XV by Ian Madigan, who performed well when he came on against the French.

Joe Schmidt's Irish team topped Pool D last week, ahead of second-placed France, who were comprehensively beaten by defending champions New Zealand in their quarter-final at the Millennium on Saturday.

But that win came at a cost. Firstly talismanic lock and skipper Paul O'Connell and flanker Peter O'Mahony sustained tournament-ending injuries. Then star flanker Sean O'Brien picked up a one-week suspension for punching Pascal Pape.

Iain Henderson, who has had an outstanding tournament, comes in to the second row to partner Devin Toner, with Jordi Murphy and Chris Henry filling the flanking vacancies left by O'Mahony and O'Brien. Jamie Heaslip captains the side from No 8.

- Do-or-die -

Argentina reached the last four in the 2007 World Cup having beaten Ireland in the pool stage and they have looked a dangerous team this time around.

Having gone down 26-16 to Pool C winners New Zealand in their opener, they pulverised the rest of the group opposition.

Scrum-half Martin Landajo is one of a host of regulars recalled by coach Daniel Hourcade after a second-string side posted a 64-19 win over Namibia in their final pool game last week.

Landajo will be partnered at halfback by Nicolas Sanchez, veteran Juan Martin Hernandez lining up in midfield alongside Matias Moroni, playing in the absence of the suspended Marcelo Bosch.

"It's a do-or-die game, very tough and tricky," said Hourcade. "It's the game we were all hoping for, for which we were preparing and there are no surprises.

"Ireland have confirmed what they've been doing over the last two years, winning the last two Six Nations, clearly the best and playing very well."

Hourcade said Ireland missing a trio of first-choice players would "change nothing".

"Obviously those that are absent are well known and the replacements less so, but they are first class and showed that against France.

"The challenge is to translate what we are doing on the training paddock into reality," he said. "It is a defining moment. Now is when we must remain faithful to our game, to follow our gameplan and make the least number of errors."

Ireland had a slight hiccup against Italy in pool play, a hard-fought match eventually going their way 16-9. And Schmidt said he and his coaching team had taken good note.

"We've tried to build each match and it doesn't always work," acknowledged Schmidt.

"Italy for us was a very tough day at the office, they made it very difficult for us and there are a number of similarities in the way Italy and Argentina play.

"They tend to get in your face, challenge you at the breakdown and on top of that Argentina have the luxury of some world-class finishers and some people very adept at transferring the ball to those finishers.

"Across the board they've got a fair bit more armoury than Italy had and we struggled past Italy with a pretty full team so we know we have to go another step. Have we got that in us? We'll find out on Sunday."
Source: AFP