LONDON • Ireland face an immediate injury emergency after flanker Peter O'Mahony was ruled out of the Rugby World Cup yesterday with knee ligament damage.

And there are concerns over the participation of captain and lock Paul O'Connell (knee ligament injury) and star fly-half Jonny Sexton (groin) as they look forward to a World Cup quarter-final against Argentina on Sunday.

Joe Schmidt's team have a week to lick their wounds from the ferocious 24-9 win over France last Sunday and prepare to meet a Puma side who the coach considers "incredibly good".

The Irish outscored the French by two tries to nil thanks to Rob Kearney and Connor Murray, with contributions from the boots of Sexton and his replacement Ian Madigan. That ensured top place in Pool D.

But Sexton limped off, while O'Connell and O'Mahony were stretchered off, raising immediate doubts for Schmidt.

"It doesn't look great with Paul," said the coach. Sexton was close to tears as he walked off, but Schmidt said he probably had an adductor problem. "I've spoken to Jonny and he's already talking about next week. I'm not sure whether that means he'll be playing. He's never short of advice!"

Ireland were relieved to avoid France's fate of having to play New Zealand. But Schmidt can see a big challenge in Argentina, who opened their Pool C campaign with a narrow 26-16 defeat by the All Blacks before easily seeing off Georgia (54-9), Tonga (45-16) and Namibia (64-19).

"The biggest attraction for us playing Argentina was the seven-day turnaround, not because we want to play them," Schmidt said, with one eye on the injuries. "They've been incredibly good, not just since the Rugby World Cup started.

"We know that the physicality, the speed and the skill of the Argentinians are going to challenge us massively. Their set piece is going to be a real challenge."

AGENCE FRANCE-PRESSE