James Hook returns to the fly-half slot as Wales look to make it three wins in a row in the Six Nations tournament at the Millennium Stadium on Saturday.
Hook played at halfback and guided Wales to an impressive victory over Scotland at Murrayfield last month, but it was Stephen Jones who wore the No.10 shirt in the away win in Italy on February 26.
This time, Jones is on the bench, with fit-again Scarlets centre Jonathan Davies returning to midfield alongside Jamie Roberts after Hook deputised for him against Italy 10 days ago.
Another change from the game in Rome sees a recall for Cardiff Blues winger Leigh Halfpenny, who is preferred to the unlucky Morgan Stoddart, a try-scorer against England and Italy.
Wales coach Warren Gatland has otherwise kept faith with the team that edged the Italians and that means scrum-half Mike Phillips and No.8 Ryan Jones both will win their 50th caps.
The team announcement had been scheduled for Thursday to assess the state of various injuries, but Gatland brought this forward by 48 hours.
He will choose two from three back-five forwards - Rob McCusker, Andy Powell and Jonathan Thomas - after fitness checks on Thursday, while there is a confirmed place among the substitutes for Sale scrum-half Dwayne Peel.
Gatland will break the Wales coaching record of 35 Tests in charge on Saturday, eclipsing Alan Davies'mark. Ireland though, have only lost once in Cardiff since 1983.
"This is a crucial game for us as a win will keep us in the Championship mix and take us into that final round with everything still to play for," Gatland said.
"But it is also a big game for Ireland, who are in a similar position to us going into this match."
Addressing the fly-half issue, assistant coach Robin McBryde challenged Hook to justify the faith shown in him.
McBryde said: "The debate at fly-half will continue long after the Championship is over, but we have gone for James on this occasion.
"James provides a running threat and we will be looking for him to show he can control the game as well and help us play in the right areas."
Of Halfpenny's recall, McBryde added: "Leigh had a good run out for the Blues at the weekend, we know all about his pace and what he offers around the field as well as being solid under the high ball and giving us a long-range kicking option.
"Morgan misses out, but he has done nothing wrong and we know he can be relied on if we need him from the bench."
