Andy Farrell will await medical updates on a host of players before announcing a squad of around 37 or 38 on Wednesday afternoon for this November's fixtures against Japan, New Zealand and Argentina.
To further complicate matters, there is little by way of form to go on and much of it some way short of Test level.
The later end to the Lions tour and the removal of the first two rounds of Champions Cup matches, along with the need for squad rotation among the provinces has also muddied the waters, with a trickle of players having at most three games under their belts, most less than that and some frontliners who have yet to make their seasonal reappearances.
Into the latter category fall three Irish Lions, namely Iain Henderson, Conor Murray and Robbie Henshaw, and of those only Murray looks likely to take to the field in the final round of URC matches this weekend before the squad assembles.
Henshaw (knee) was said to have started running again on Tuesday and has previously demonstrated his ability to overcome an injury enforced absence. Ulster head coach Dan McFarland has also intimated that Henderson (thumb) should be fit for the November Tests.
In addition to the cruelly unfortunate Will Addison, three other Ulster players involved in the summer Tests have been sidelined since their round one win over Glasgow.
Again, McFarland said the trio of Jacob Stockdale, Stuart McCloskey and Robert Baloucoune were all "close" to returns.
The onset of an international window wouldn't be the same without a Johnny Sexton injury scare, albeit Leinster head coach Leo Cullen made light of the hip injury which forced the Irish captain off in last Saturday's 50-15 win over the Scarlets.
Harry Byrne is seemingly set to play this weekend after recovering from the hip injury he suffered last Saturday week against Zebre, which could contrive to see Jack Carty and Billy Burns miss out.
Digging further into Leinster's vast reserves, it would be no surprise if their dynamic young hooker Dan Sheahan is named in the squad.
Despite seemingly usurping Ryan Baird the decidedly in-form Ross Molony could conceivably miss out given the previous investment in Baird, as might the in-form Ultan Dillane also, given the emergence of Fineen Wycherley.
Backrow is, as ever, ridiculously competitive. Such has been the form of two of the summer debutants, Gavin Coombes and Nick Timoney, that they might nudge out the likes of Paul Boyle, Dan Leavy, Rhys Ruddock and Jack O'Donoghue.
Nathan Doak's time will come but probably not just yet on the basis of four eye-catching URC outings, especially considering four other capped scrumhalves could also miss out – Caolin Blade, Kieran Marmion, Luke McGrath and John Cooney.
Presuming Henshaw and McCloskey are named, the absence of Chris Farrell could leave room for at least one of the younger likely lads, with James Hume perhaps leading the queue ahead of Ciarán Frawley and Stewart Moore after his impressive Test debut against the USA.
Last, but by no means least, it will be intriguing to see if the injuries in the back three will create an opening for Simon Zebo. Somewhat under used in his two and a bit outings by Munster on the left wing, despite two tries on his prodigal return, Zebo brings an X-factor, left boot, versatility and eye for the try line which few possess.
The Irish squad might, or might not, look something like this
Hookers: Kelleher, Herring, Sheahan.
Props: Porter, Kilcoyne, Healy, Furlong, O'Toole, Bealham.
Locks: Ryan, Henderson, Beirne, Baird, Wycherley.
Backrows: Doris, Conan, Van der Flier, O'Mahony, Coombes, Timoney.
Scrumhalves: Murray, Casey, Gibson-Park.
Outhalves: Sexton, Carbery, H Byrne.
Centres: Aki, Henshaw, Ringrose, McCloskey, Hume.
Back three: Keenan, Earls, Larmour, Lowe, Stockdale, Conway, Zebo.
