Jordan Larmour faces the biggest challenge of his fledgling Test career when starting Ireland's World Cup opener against Scotland at full-back.
The 22-year-old Leinster speed merchant will make just his seventh Test start when slotting into Ireland's starting XV with Rob Kearney unable to fend off his calf problem.
Andrew Conway will start on the wing with his Munster team-mate Keith Earls not fully fit after a thigh complaint.
Assistant coach Andy Farrell declared both Kearney and Earls "available for selection" on Wednesday, but Ireland have opted not to risk either senior star in their pivotal Pool A battle.
Larmour's toughest task could be to stay strong under the high ball, the much-vaunted young star needing to hit top form to match one of Kearney's chief assets.
Conway has impressed across Ireland's warm-up matches and has always proved hugely reliable under the high ball.
So the 28-year-old will doubtless be called upon to help Larmour cope with the expected aerial assault.
Garry Ringrose has edged out Chris Farrell to start at outside centre, with Robbie Henshaw missing out due to hamstring trouble.
Rory Best captains the side from hooker on his 121st cap, while Iain Henderson will partner James Ryan at lock, with Tadhg Beirne on the bench.
Jack Carty is preferred to Joey Carbery on the bench, but Joe Schmidt confirmed that Munster playmaker Carbery is fully fit.
Schmidt said Earls and Kearney are fit but had not quite shaken off their injuries to have enough training time to merit selection.
"Keith Earls was the sharpest player on Wednesday at training," he commented.
"He's good and Rob Kearney trained well as well.
"We were really just getting tight for time. The best continuity we had was to have the guys we'd had training through the time we were here.
"It's exciting to have the back three we've got as well. It's a great opportunity and a fantastic challenge."
— Irish Rugby (@IrishRugby) September 20, 2019
Ireland team to play Scotland
Forwards: 1 Cian Healy (Leinster), 2 Rory Best (CAPTAIN, Ulster), 3 Tadhg Furlong (Leinster), 4 Iain Henderson (Ulster), 5 James Ryan (Leinster), 6 Peter O’Mahony (Munster), 7 Josh van der Flier (Leinster), 8 CJ Stander (Munster)
Backs: 9 Conor Murray (Munster), 10 Jonathan Sexton (Leinster), 11 Jacob Stockdale (Ulster), 12 Bundee Aki (Connacht), 13 Garry Ringrose (Leinster), 14 Andrew Conway (Munster), 15 Jordan Larmour (Leinster)
Replacements: 16 Niall Scannell (Munster), 17 Dave Kilcoyne (Munster), 18 Andrew Porter (Leinster), 19 Tadhg Beirne (Munster), 20 Jack Conan (Leinster), 21 Luke McGrath (Leinster), 22 Jack Carty (Connacht), 23 Chris Farrell (Munster)