Sunday's win against France was a costly one for Joe Schmidt.
25 minutes into the first half, Johnny Sexton was forced from the pitch due to a combination of an abductor injury and a shuddering hit from Louis Picamoles. Sexton may yet be fit to face Argentina, but with Ian Madigan proving an able deputy against the French, fears over the out-half position have already been partially allayed for the quarter-final.
Schmidt's real problems come in the pack. Peter O'Mahony has been ruled out for the remainder of the tournament due to knee ligament damage, replaced in the squad by Rhys Ruddock.
Paul O'Connell's tournament - and likely Ireland career - is over due to what is thought to be a severe hamstring injury. Mike McCarthy is reportedly the man who will takes the Ireland captain's place in the squad.
The Ireland head coach's final and most frustrating selection issue for the quarter-final is who to play at openside. Due to the collision of his right hand with Pascal Pape's abdominal area, Sean O'Brien has been cited and will likely miss Sunday's game.
It leaves Schmidt with some big selection decisions for this weekend, namely at second row, blindside and openside.
Speaking on Off the Ball on Monday night, Brian O'Driscoll outlined what his selection would be. O'Driscoll named Iain Henderson at six - due to his ball carrying ability, Chris Henry at openside and finally, Donnacha Ryan in the second row.
I think because it's Argentina - if you don't have Seanie, Chris Henry goes in automatically. I thought he made a really good impact off the bench for Pete. He's been a guy who's made a big difference when he's come on. Against some of the smaller nations, he had a good contribution. You get a different player with Chris, more of a link player and a groundhog.
I think you have to go for some size in your back row. That's why I reckon Iain Henderson might start at six and then bring Donnacha Ryan into the second row along Dev Toner. Donnacha Ryan brings a hard edge like Paulie has. He'll be keen having not gotten a huge amount of game time.
I think you have to go with an explosive ball carrier, if you're losing Seanie. Depending on what happens Cian Healy, whether they start him or bring him off the bench, you need one really explosive ball carrier and that's where - at six - Henderson will get more of an opportunity to carry.
Listen to O'Driscoll on Off The Ball below.
