Hamstring injury sidelines Robbie Henshaw for Ireland clash against Argentina
Ireland must face Argentina without midfield linchpin Robbie Henshaw after the British and Irish Lions centre suffered a hamstring strain in training.
Munster's Chris Farrell will replace Henshaw for Saturday's Aviva Stadium clash, winning just his second Test cap at outside centre.
Four of Ireland's starting backline boast just five caps between them, with head coach Joe Schmidt accepting his revised line-up faces a hefty challenge against the dangerous Pumas.
Boss Schmidt has restored a raft of frontline stars following last weekend's experimental XV for the tight 23-20 win over Fiji, but Leinster wing Adam Byrne will make his Test debut on the wing.
"He's got a slight hamstring strain," said Schmidt, of Leinster centre Henshaw.
"I think at a push he could potentially have been involved.
"But it should see him fine for what's coming up, he's got a busy period coming up.
"This window was a chance to see how guys do in pressure situations.
"Chris (Farrell) acquitted himself pretty well last week, got better as the game went on, and it's another opportunity for him.
"Adam Byrne has given us the confidence to include him because he's worked really hard and has been picking things up all the time in training.
"With a bit of experience around him I'm hopeful he'll have a good first hit out in an Irish jersey.
"There's a host of threats out there for Argentina so it will be a really challenging day for those outside backs.
"Four of those outside backs have just five caps between them.
"But again, it's all about challenging them to step up."
Conor Murray, Johnny Sexton and Rob Kearney will be charged with keeping the inexperienced Byrne, Farrell, Bundee Aki and Jacob Stockdale in check in Ireland's new-look backline.
Leinster's fast-improving 21-year-old lock James Ryan has been handed his first Ireland start, for his fourth cap, in a chance to showcase his burgeoning talent once again.
Schmidt and back-rower Peter O'Mahony tipped lock Ryan for a big impact this weekend.
"He's only really dipped his toe into the water so far, but this is a big chance to find out more about him, and that's what this window is all about," said Schmidt, of Ryan.
Flanker O'Mahony echoed Schmidt's feelings, saying of Ryan: "He's intelligent and tough, but he gets stuck in when he's asked to. And he's been quite impressive."
Ireland will face Argentina on Saturday for the first time since their 43-20 World Cup quarter-final humbling in Cardiff in 2015.
Asked if this rematch represents a grudge encounter, Schmidt said: "Not at all.
"If we're looking two years backwards how do we go forwards? We're looking forward to what we can learn from the game.
"There's a real danger in looking too far backwards.
"It's just about trying to get a bit of cohesion, there's new combinations, we'll be a lot more focused on ourselves than Argentina."