Rare indeed is the opening selectorial offering of the season so changed - nine positional and two in personnel from the draw with Canada last summer - yet at the same time so predictable. Indicative of the changed times perhaps is that Denis Hickie ranks as the second oldest member of the back-line at 24.
Curiously, only Peter Stringer and Shane Horgan survive from the Canadian game in a quick and youthful back-line, and even there Horgan is switched from his converted role on the right wing (where he has won his five caps and scored five tries) to his more established position of inside centre for the first time at Test level.
Geordan Murphy and Tyrone Howe, both blooded in the second Test of the Americas' tour last summer against the USA Eagles, will make their home debuts, while Hickie and Brian O'Driscoll are back from injury and Ronan O'Gara is preferred to David Humphreys.
In contrast to the baby-faced backs, the pack has a gnarled and grizzled look to it, thanks in part to an unexpected recall for Paddy Johns following injuries to Mick Galwey and, out of the blue, Jeremy Davidson.
Though the Castres captain hadn't realised it, Davidson had broken a scaphoid bone at the top of his hand fully four weeks ago. But, having played with it, difficulties in lifting weights in training on Monday prompted the Irish medical staff to send him to hospital for a scan, whereupon the break was detected.
Just as well, too, or he might ultimately have missed the whole season. As it is, Davidson will be in plaster until almost Christmas but should be back in the New Year.
So Johns makes his first start for Ireland in over a year, dating back to the win over Romania in last year's World Cup, while the uncapped Gary Longwell - supposedly called into the squad, co-incidentally, as cover for Johns due to the latter's sore throat - is on the bench.
It was not the most difficult selection meeting, as Warren Gatland conceded. "There's an opportunity for a few players in this game with Japan, and looking towards South Africa and the Six Nations, particularly with Shane Horgan. He hasn't been tested at international level in midfield, and we just want to have a look at that combination with Brian O'Driscoll, which has worked well for Leinster. We were delighted with Rob Henderson last year, we know what he can do, and now we want to see what Shane can do."
Likewise, this was a gilt-edged chance to look at Murphy, and, as Brian O'Brien maintained, it's a form selection, the prime example being the whole-hearted Howe.
"Tyrone's forte would be his total honesty, and any ability he has he uses to the fullest," observed O'Brien. "He's certainly a team player, as his form with Ulster has indicated."
The most contentious call - in the absence of the injured Simon Easterby - was arguably at number six, where Andy Ward will win only his third cap of 25 as a starting blindside flanker, in preference to Eric Miller, who has been playing there all season for Leinster.
"Well, Eric's only got into the Leinster team in the last couple of matches," said Gatland. "We've been impressed with Andy for Ulster. I've expressed on a number of occasions that I don't believe he's an out-and-out seven, that he is probably a six-and-a-half. We're looking at him in terms of his ball-carrying ability. "I think Eric has been impressive lately and is playing himself into some real form, and I think with the back-line we've picked a couple of players, such as Kieron Dawson and Ward, who can give us some real continuity."
The decision at outhalf will always be something of a toss-up as long as O'Gara and Humphreys are in good form and good health, though this time the Americas form guide was at least partially applied.
"If we look back on the Canadian game, David didn't have the greatest game and Ronan did very well when he came on," commented Gatland. "Perhaps the results of Munster this season give Ronan the edge in terms of confidence. He probably has that bit more ability to shut down a game at the moment, but in terms of footballing ability there's not a heck of a lot between the two of them and we'd be happy with either one of them in that position at the moment."
Keith Wood will captain the side on the occasion of his 40th cap, while the 40th appearance of the non-drinking, non-smoking, pure-as-the-driven-snow Peter Clohessy (nothing is sacred anymore) will be marked by the appearance of his son Luke, aged seven, as the team mascot. That the young Clohessy will be led out by Wood would be appropriate, for Luke cites Uncle Fester as his favourite player, with dad second. That's sons for ye.
Tickets for the Ireland-Japan game (with stand tickets reduced to £20) are still available from www.ticketmaster.ie or from the IRFU ticket line on 1890 925120.
