Jordi Murphy only touched down in Japan on Sunday but will wear the Ireland no 8 jersey against Russia on Thursday.
The versatile Ulster back row was called into the squad to replace the injured Jack Conan and, due to Rugby World Cup rules, only joined up with Joe Schmidt's squad yesterday afternoon.
Barring any last minute injuries in training this morning, Schmidt will retain only four of the starting line-up that were shocked by Japan.
With Rory Best rested, Johnny Sexton will lead the team out in Kobe against the Pool A minnows. Peter O'Mahony is the only surviving pack starter from the Shizuoka shocker.
There will be an all-Munster front five with Dave Kilcoyne, Niall Scannell and John Ryan in the front row, and with Jean Kleyn making his World Cup debut in the second row beside Tadhg Beirne.
Murphy is joined in the back row by O'Mahony, who switches from the blindside to openside in place of Josh van der Flier, with Rhys Ruddock wearing the no 6 jersey.
Sexton returns as captain as Ireland looks to reassert themselves as an attacking force against minnows Russia, who have already lost to Japan and Samoa.
Conor Murray is rested after starting twice already in the pool games and Sexton's half-back partner will be Luke McGrath.
Schmidt has made four changes to the backline in total. Rob Kearney remains at full-back after passing his concussion test.
Andrew Conway returns to the wing after his outstanding display against Scotland, replacing Jacob Stockdale. Keith Earls retains his place in the back three.
Garry Ringrose keeps the no 13 jersey and will be partnered by Bundee Aki, who replaces Chris Farrell - a concussion in the Japan defeat ruled him out.
Robbie Henshaw won't make his first tournament appearance until the final pool encounter with Samoa.
IRELAND: R Kearney, A Conway, G Ringrose, B Aki, K Earls, J Sexton, L McGrath; D Kilcoyne, N Scannell, J Ryan, T Beirne, J Kleyn, R Ruddock, P O'Mahony, J Murphy.
Replacements to be announced.
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