Kobe - World Player of the Year Jonathan Sexton will captain Ireland for the first time after being recalled for their Rugby World Cup match against Russia on Thursday following a thigh injury.
The 34-year-old fly-half missed Ireland's shock 19-12 defeat by hosts Japan in Shizuoka on Saturday, which threw Pool A wide open, with a knock he suffered in the opening 27-3 win over Scotland.
British and Irish Lions star Sexton was one of 11 personnel changes and two positional switches made by Joe Schmidt following a five-day turnaround, in what is the New Zealander's last tournament before he steps down as Ireland coach.
"It's a massive honour. I spoke to Joe this morning, so I only found out myself over the last few hours," Sexton told reporters after Schmidt announced the team on Tuesday.
"I haven't even had a chance to tell my family or anything, but I'm sure they're going to be very proud as well."
The Leinster playmaker added: "It's something that I've thought about since I was a kid, something I've made a lot of decisions around trying to get there one day.
"It has taken a while but it was worth the wait and I'm incredibly proud.
"I want to be captain now of a good performance and a good win in a World Cup game, so that's my main focus.
"I have a big responsibility in the team anyway, so nothing has changed," insisted Sexton, who said he was also fit enough to resume his role as Ireland's first-choice goal-kicker.
Schmidt, explaining why he had made so many alterations, said: "There might be 13 changes because we do need to make sure everyone is ready and involved as much as possible, to get everyone up to speed.
"It's pretty tough with a six-day and then a five-day turnaround, there's always going to be a bit of attrition. We're looking to freshen it up and give guys an opportunity.
"It's great, because we've got some guys who would have been very, very keen to be involved who will get an opportunity on Thursday."
Schmidt gave Jordi Murphy an immediate start at No 8, with the back-row having only recently arrived in Japan to replace the injured Jack Conan in the 31-man squad.
"He trained unbelievably well today," Schmidt said.
"He is straight off the flight, he got in late Sunday.
"We are just asking for him to do the best he can for us. The one thing with Jordi is that you seldom get anything other than that. He's a really good performer for us and we'd have a lot of confidence about him being able to slot straight in."
Meanwhile centre Garry Ringrose and flanker Peter O'Mahony will both be starting their third game in 11 days when Ireland face Russia in what are set to be sweltering conditions under the closed roof of the Kobe Misaki Stadium.
Ringrose will partner the returning Bundee Aki in midfield, with Chris Farrell ruled out due to concussion and Robbie Henshaw still to regain full fitness following hamstring trouble.
Up front, Ireland will field an all-Munster front-five against Russia.
They will now look to beat both Russia and Samoa in their two concluding group fixtures and may well need bonus points from both to be certain of gaining one of the two quarter-final spots on offer from a tightly-contested Pool A.
Ireland will have to make history if they are to be crowned world champions for the first time, as every side that has lifted the Webb Ellis Cup has gone through the tournament unbeaten.
The Pool A match at the Kobe Misaki Stadium is scheduled for 12:15 (SA time) on Thursday.
15 Rob Kearney, 14 Andrew Conway, 13 Garry Ringrose, 12 Bundee Aki, 11 Keith Earls, 10 Johnny Sexton (captain), 9 Luke McGrath, 8 Jordi Murphy, 7 Peter O'Mahony, 6 Rhys Ruddock, 5 Jean Kleyn, 4 Tadhg Beirne, 3 John Ryan, 2 Niall Scannell, 1 Dave Kilcoyne
Substitutes: 16 Sean Cronin, 17 Andrew Porter, 18 Tadhg Furlong, 19 Iain Henderson, 20 CJ Stander, 21 Joey Carbery, 22 Jack Carty, 23 Jordan Larmour