They'll surely be happier that it's the world champions they are facing rather than Jamaica, the team that had been provisionally pencilled in by the FAI for this game, Emmet Malonereports
But after a few days of trawling through Brian Kerr's apparently extensive collection of Brazil videos, it seems safe to assume that the players he tells this morning are in his starting line-up will feel more than a hint of trepidation as they await kick-off time at Lansdowne Road tonight.
At the weekend Sven-Goran Eriksson recalled the second half of England's game against the Brazilians as the low point of his time in the job. "We ran and ran and ran, he sighed, "but never had the ball."
Watch the South Americans in full flow for just a few minutes and it is easy to see how such a fate could befall a much better team than his.
For Kerr any sort of a result against a team of such quality would be a decent achievement and the reality is that Ireland could lose and still emerge from the encounter with a good deal of credit.
The real challenge for the manager, though, is to strike the right balance between his need to get rebuilding for the autumn and the desirability of players taking something positive from an encounter with opponents of much the same class as the French side they must face twice during the forthcoming World Cup qualifying campaign.
Kenny Cunningham joked yesterday that he had given up watching Spanish football in recent weeks so as to avoid seeing Ronaldo in action but the Irish skipper went on to discuss the importance of taking the game to the Brazilians and displaying the sort of confidence and composure that would normally be expected of an Irish team on home soil.
Whether they can manage it would appear to depend to a large extent on just how the Brazilians apply themselves, although after yesterday's somewhat chaotic training session at Lansdowne Road their manager, Carlos Alberto Parreira, insisted that, with no further opportunities to prepare his players between this and their next World Cup qualifier at the end of March, his side would not be taking things lightly.
"It is difficult to let things go and then just pick them up again," he said. "That is why we look to play our strongest side in every game. The challenges involved in this game," he added, "will be different to those we encounter in the qualifiers against other South American sides but everybody wants to beat Brazil and so every game is tough which is why we go into them with the same attitude."
The upshot is that Parreira is likely to field much the same side that beat Germany to lift the World Cup a little over 18 months ago. The new manager has tinkered a little with the formation but the personnel have a very familiar look about them with Rivaldo, who struggled after the finals to maintain the outstanding form he showed for Brazil, the most noticeable absentee from the summer before last.
In his place Parreira can call on Kaka, Milan's magical young star, to compliment a strikeforce that also includes two of the world game's most talented forwards. To say the Irish back four will have to be at their best may, in the circumstances, be to stray into the realm of understatement.
So many times in the past at Lansdowne Road, however, Irish sides have defied the world rankings and matched teams that should have been too good for them. If it is to be done again then the hosts must manage to pose a persistent threat to a defence and, as importantly, a midfield who can do untold damage if allowed to retain comfortable possession.
With his most creative player, Damien Duff, ruled out through injury, it will not be easy but Kerr may well choose in the circumstances to hand Andy Reid his second international cap and grant him the sort of freedom that the Chelsea winger generally puts to good use at this level.
With Gary Breen also out the manager must choose between Richard Dunne, Andy O'Brien and, possibly, John O'Shea for his second centre half. Dunne, of course, could point to the unexpectedly efficient job he did on Patrick Kluivert in Amsterdam a few years back and Kerr certainly has a soft spot for the big Manchester City man.
O'Shea has been playing in the role more of late too but it could be that, with the Waterford man still preferred at left back, O'Brien's 18 Champions League and UEFA Cup matches for Newcastle over the past couple of seasons may mark him out as the man for tonight's task.
Kerr insisted once again yesterday that those who will be passed over this evening will get their chance during the months ahead, several of them against the Czech Republic next month. After waiting so long for his return, however, Jason McAteer seems set to return to the Irish side with the only question appearing to be whether he is allowed to play in the centre of midfield or returned to the right flank.
The player's own preference is clearly for the centre but Kerr has talked about him recently as having been the most consistent performer in the wider position during Mick McCarthy's time in charge.
If Matt Holland succumbs to the neck injury that prevented him training yesterday then there may be little choice and either Reid or Steve Finnan will start on the wing but if the Charlton midfielder is declared fit today then McAteer may indeed, as he joked at the weekend, find himself running at Roberto Carlos "with two dodgy hamstrings".
Given Robbie Keane's recent form and Brazil's knack, despite the undoubted quality of their back four, for conceding goals, the home side are certainly capable of scoring at least once, as they have done in each of their six home games under Kerr.
Quite how they fare at the other end, however, is likely to determine the outcome of what could be, in contrast to most friendly games, a genuinely memorable encounter.
REPUBLIC OF IRELAND(probable): Given (Newcastle Utd); Carr (Tottenham), Cunningham (Birmingham City), O'Brien (Newcastle Utd), O'Shea (Manchester Utd); McAteer (Sunderland), Kavanagh (Cardiff City), Holland (Charlton Ath), Reid (Nottingham Forest); Morrison (Birmingham City), Keane (Tottenham).
BRAZIL: Dida (AC Milan); Cafu (AC Milan), Roque Junior (Siena), Lucio (Bayer Leverkusen), Roberto Carlos (Real Madrid); Kleberson (Manchester Utd), Gilberto Silva (Arsenal), Ze Roberto (Bayern Munich), Kaka (AC Milan); Ronaldinho (Barcelona), Ronaldo (Real Madrid