Manager Mick McCarthy's old hands were in the end more influential than the so-called Young Dubs he has recently introduced, but both the long term and the immediate future looked bright again on a rousing Dublin afternoon.
After two narrow failures in the most recent major tournaments, going out on a play-off each time, the Republic have uncovered a crop of bright young players in every age group. In the summer, they became the first country ever to win the European Championship at both Under-18 and Under- 16 level.
The first graduate from those sides, Robbie Keane of Wolves, played his first competitive game for the seniors yesterday and although any comparisons with Michael Owen may prove unwise, he was very much in McCarthy's mind when the manager said earlier in the week: "The guts of this team could be together for 10 years."
It was Keane's namesake Roy who made the greater impression yesterday, producing a driving midfield performance on his return after a year's absence. Along side him Mark Kinsella was as impressive as he has been in Charlton's opening Premiership games, while the experience of Irwin, Steve Staunton and Jason McAteer shone through when it mattered.
It was vital to the Republic's hopes of success in the group to begin well before travelling to Yugoslavia next month, as McCarthy acknowledged afterwards. "We played well and deserved to win," he said. "We've started with a good victory but it's only a start."
As fortune has not always favoured him since succeeding Jack Charlton two and a half years ago, the manager could not be begrudged his luck in playing Croatia at a time when players like the World Cup's leading scorer Davor Suker, Alen Boksic, Goran, Vlaovic, all strikers, Robert Prosinecki and Slaven Bilic were all unavailable.
Without them, Miroslav Blazevic's side badly needed to subdue the home team and another full house of 34,000 early on, rather than conceding a penalty within five minutes of the kick-off.
Having already twice thrust forcefully down the left, the Irish switched to the right, where Jason McAteer sent Irwin away on the overlap. Although his cross came to nothing, the Manchester United full-back, challenging for possession again, found himself sandwiched between Robert Jarni and Krunoslav Jurcic.
If it was the kind of penalty award that falls to home teams more often than visitors, Irwin was not about to refuse the gift and calmly placed his kick low to the goalkeeper's left for, surprisingly, only his third goal in 49 internationals.
Keith O'Neill, the Norwich striker, was off the pitch having treatment on a leg injury while the penalty was taken and he returned for only a few more minutes before being replaced by Tony Cascarino, still domiciled in France.
The 36-year-old, even more of a physical presence than O'Neill, immediately put himself about and it was a swirling cross from McAteer aimed towards him that led indirectly to the second goal. The ball was overhit, but Igor Tudor, the right wing-back, unnecessarily conceded a corner, which was cleared only to McAteer some 20 yards out. His fierce drive was deflected into the air and Roy Keane out-jumped everyone to head inside the far post.
After setting up McAteer soon after halftime for a shot just passed the post, Robbie Keane made way for Lee Carsley in a substitution designed to bolster the midfield, which almost brought a third goal instead.
Keane had barely made it to the dugout as Irwin swung over a free kick that goalkeeper Drazen Ladic pushed out unconvincingly. The ball fell perfectly for Carsley, whose first touch in the match was a 20-yard drive heading for the top corner of the net until Ladic pushed it away. From the resulting corner Kinsella thumped a shot against the bar from similar range.
A header by substitute Egor Pamic straight at Shay Given suggested a possible recovery by the Croats, which was soon undermined when two of their number were sent off within as many minutes. First Mario Stanic went in late on Staunton and received his second yellow card. Then Jurcic, absurdly, lunged at the same opponent and the Portuguese referee brought out the red card.