Joe Schmidt to trim World Cup squad by up to seven players next week
Head coach Schmidt has been at pains to leave Ireland's options as open as possible in the long build-up to September's global showdown, but conceded the time for tough decisions is nigh.
Schmidt has retained 45 players in his training squad but will start whittling that down following Saturday's warm-up clash against Wales in Cardiff.
Ireland must name their final 31-man World Cup squad on August 31, with home and away Tests against Wales and a Dublin battle with Scotland all to come in advance.
"I want to have my mind made up now: it would make it a lot easier!" said Schmidt regarding World Cup selection.
"There are some really tough decisions.
"Over the next week or so that inevitably has to happen.
"We've got to hone the group and those decisions are tough enough without even looking at the 31.
"We might end up with 38 or 39 in a week's time, and then we have to take it from there again."
Donnacha Ryan and Keith Earls will both end 29 months without Test rugby when they start Ireland's Cardiff clash this weekend.
The luckless Munster duo's catalogue of injuries has kept both from Test action in Schmidt's coaching era, but now both men can state their World Cup selection case at the Millennium Stadium.
Lock Ryan and centre Earls will make their first Test appearances since the 22-15 defeat in Italy in March 2013, with Jamie Heaslip and Mike Ross the sole frontline stars on show.
Ryan admitted he feared his Test career was already over as he battled a long-term toe injury branded "weird" by Munster boss Anthony Foley last season.
"Without being too dramatic about it yes, I did think I may not get another chance," said Ryan.
"Pre-season is always quite tough so I've just got to empty the tank and it's as much mental strength as anything."
Ireland's Kiwi boss Schmidt denied Saturday represents the one and only opportunity for a clutch of stars to prove their World Cup worth.
The former Leinster boss branded the Cardiff match "the biggest examination" after a gruelling six-week training stint.
For men like Ryan, Earls and Ulster centre Darren Cave however, this could well be their sole opportunity to force Schmidt's selection hand.
"I wouldn't say it's the one opportunity, they've worked really hard and we've taken note of how they've trained," said Schmidt.
"It's a very narrow window, but it is the litmus test, it is where we find out whether they can stay in the game and physically and mentally deliver what is required.
"It's probably the biggest examination but it's been an examination over the last six weeks."
Schmidt also admitted Cian Healy's protracted recovery from neck surgery could pose a selection conundrum further down the track.
Ireland face England on September 5, before opening their Pool D World Cup account against Canada on September 19.
Schmidt conceded he remains unsure what approach he would take should Healy look likely to miss the England game but be expected to be ready to face Canada.
"We're just hoping the picture gets clearer as we get closer so that we can make a decision that would see him fully fit at least to start the tournament," said Schmidt.
"We play two weeks prior to the first game so if we thought he might not be fit for England but he would be fit for Canada I'm not sure what we'd decide."
Ireland team to face Wales in Cardiff on Saturday:
F Jones (Munster), A Trimble (Ulster), K Earls (Munster), D Cave (Ulster), F McFadden (Leinster), P Jackson (Ulster), E Reddan, J McGrath, R Strauss, M Ross (all Leinster), D Ryan (Munster), I Henderson (Ulster), J Murphy, T O'Donnell, J Heaslip (capt, all Leinster).
Replacements: R Best (Ulster), D Kilcoyne (Munster), M Bent (Leinster), D Tuohy, C Henry (both Ulster), K Marmion (Connacht), I Madigan (Leinster), S Zebo (Munster).