As an initial stab, here’s my guess for Ireland squad with a couple of options in 2-3 positions - all coming from Connacht who have improved greatly this season.
With Luke McGrath definitely out, and a question mark over when Kieran Marmion can return, his understudy, Caolin Blade at Connacht should be a deserved shout. Blade and outhalf Jack Carty have been the best form halfback pairing of the Irish teams this season in my view. And if we lose a 10 between now and Japan, Carty is well-worth considering as a back-up. Ultan Dillane has recovered some of his earlier career form and could oust his Connacht team-mate Quinn Roux to get a lock spot. Ditto Finlay Bealham instead of Munster’s Kilcoyne. One other Connacht player who might be considered is midfielder, Tom Farrell, who partners Aki in the Westerners first team.
Hookers: Best, Cronin, Scannell.
LH: Healy, McGrath, Kilcoyne/Bealham,
TH: Furlong, Porter, John Ryan.
Locks: James Ryan, Toner, Beirne, Henderson, Dillane/Roux.
Back-rowers: SOB, POM, Stander, vdF, Conan, Murphy, Leavy, Ruddock.
Scumhalves: Murray, Cooney, Marmion/Blade.
Outhalves: Sexton, Carbery, Byrne/Carty.
Centres: Henshaw, Aki, Ringrose, Chris Farrell/Tom Farrell
Back three: Conway, Stockdale, Earls, R Kearney, Larmour, Addison.