Their coach, Mick McCarthy, who often cuts a lugubrious figure, seemed as buoyant as Jolly Jack himself in naming a side comprising nine Premiership players in defence and midfield, plus two of the First Division's most highly regarded strikers, Robbie Keane, of Wolves and Keith O'Neill, of Norwich.
While making all the right noises about not underestimating a country that finished third at the World Cup, McCarthy must privately be delighted with the problems faced by his opposite number Miroslav Blazevic. One of the few coaches to enhance his reputation - and keep his job - this summer, he must do without the injured strikers Davor Suker, Alen Boksic and Goran Vlaovic as well as Everton's Slavan Bilic and the gifted midfielder Robert Prosinecki, who says he no longer wants to play for Blazevic.
Croatia can still call on figures as familiar, and formidable, as Derby's Igor Stimac and his former club-mate Aljosa Asanovic (now with Panathinaikos), Robert Jarni, who spurned Coventry for Real Madrid, Milan's Zvonimir Boban and the newcomer Igor Tudor, who joined Juventus after the World Cup.
But McCarthy believes that the Republic's mixture of solidity and flair, experience and youthful brio should mean a serious challenge in a group that also includes Yugoslavia, Macadonia and Malta. "It's taken two years to put an international squad together, but we've got 20 players here who know what's expected of them," he said. "I'd love to have had this side going into the last World Cup campaign."
This game, and the trip to Yugoslavia next month, will be crucial, as much in setting the tone and fully winning over the public again as for the points at stake against the two strongest adversaries.
The Republic supporters would welcome confirmation over the next two matches that the bad old days of watching everyone else compete at the major tournaments have not returned permanently.
They would also love a new hero or two and have great expectations of the 19-year-old Keane. Now playing as an out-and-out striker for Wolves alongside Steve Bull, he will form what looks an exciting partnership today with O'Neill. "Michael Owen has proved that genuine pace is something that unsettles even the best organised defences," said McCarthy. "Robbie Keane has that kind of asset.
"Keith O'Neill has been out for almost two years with injuries. We've missed him, his pace and strength."
Like Keane, the midfielders Damien Duff and Mark Kinsella will be playing their first competitive games for their country as part of a group known as the "Young Dubs". They will be partnered in the middle by Jason McAteer and Roy Keane, the latter stripped of the captaincy early in McCarthy's reign but now forgiven and welcomed back for his first international since last September's World Cup tie in Lithuania.
There is plenty of experience behind them in full-backs Denis Irwin (48 caps) and Steve Staunton (74) with Phil Babb and Wimbledon's Kenny Cunningham in the centre of defence.
McCarthy has said that if offered a draw in advance of the match, he would not take it. Third in the world or not, sharing the points would look a good result in the circumstances for Croatia.
REPUBLIC OF IRELAND: Given (Newcastle); Irwin (Manchester Utd); Cunningham (Wimbledon); Babb (Liverpool); Staunton (Liverpool); McAteer (Liverpool), Roy Keane (Manchester Utd), Kinsella (Charlton), Duff (Blackburn); O'Neill (Norwich), Robbie Keane (Wolves).
CROATIA: Ladic (Croatia Zagreb); Simic (Croatia Zagreb), Soldo (VfB Stuttgart), Stimac (Derby); Jurcic (Croatia Zagreb), Tudor (Juventus), Boban (Milan), Asanovic (Panathinaikos), Jarni (Real Madrid); Maric (Croatia Zagreb), Stanic (Parma).