The All Blacks halfback dynamic has shifted several times this year and will do so again in the final two tests of the season.
Prior to last week's scrappy victory against Italy the All Blacks were content to finish the season without Aaron Smith.
Injuries to Brad Weber and FinlayChristie in Rome immediately changed that picture, however. Weber suffered a broken nose early in the match and while he has since presented symptom free, he must satisfy an independent concussion process to take any further part in the tour after failing his initial HIA.
Christie, in his fifth test, enjoyed his most prominent role of the elongated tour last week after replacing Weber in the ninth minute.
The Blues halfback has seized his limited chances this test season, impressing with his speed to the base, support play and committed defence. He, too, had a scare post-match, though, when he presented with a neck complaint similar to the debilitating bulging discs that heavily hindered his development at the Blues over the past two years.
That injury, suffered while playing for Tasman in 2019, stripped him of strength and forced him to reshape his passing action off his non-favoured side.
With Weber and Christie's availability uncertain at the start of this week the All Blacks were faced with the prospect of TJ Perenara being their only fit halfback for Ireland.
At that point, the All Blacks decided to take the pragmatic approach and call up Smith, who, having skipped the Rugby Championship and northern tour to be present for the birth of his second son Leo, was itching to rejoin the team.
Smith arrives mid-week in Dublin and is unlikely to be involved this weekend. A scan has since cleared Christie of any structural damage, leaving him likely to deputise for TJ Perenara off the bench in the biggest occasion of his career at a sold-out Aviva Stadium.
The All Blacks have adopted a cautious approach to head knocks this season, often ruling those players out early in the week. Even if Weber is given the green light, he is therefore expected to be held back. The knock comes at a cruel time, just as Weber sought to further his case for a start against Ireland and France.
"Right now we've got three nines in the hunt for this weekend's start," All Blacks assistant coach John Plumtree said from Dublin. "Aaron is only arriving Wednesday and he doesn't know what the plan is so it's pretty unrealistic to think he is going to be playing in the weekend.
"TJ is pretty happy with his form. All of them are going pretty well. Brad is going through the HIA protocols this week and Finlay has a little bit of an issue with his neck but he trained today so we're expecting him to be fit for the weekend."
Smith's belated presence is not expected to immediately complicate the halfback pecking order, then. Next week, though, it could create something of an awkward dynamic.
The All Blacks have been committed to Weber, Perenara and Christie since Smith stepped aside after the August 14 Bledisloe Cup victory at Eden Park. Now Smith is back in the frame, and once he overcomes his jetlag ahead of the final test of the year in Paris, the selectors face a conundrum, particularly if all four halfbacks are fit.
Smith will be short of match fitness, having only played a handful of matches for Manawatū since his last test, and is therefore likely to be competing for a bench spot against France.
Having flown him to the other side of the world before returning home for two weeks hotel isolation, the All Blacks may feel obligated to give him a run. Injecting one of the world's most influential players is also welcome luxury, of course.
That scenario could leave Perenara and Weber in a head-to-head battle for the starting role against France, with whoever misses selection potentially left out of the squad.
Other hotly contested positions this week include second five-eighth, where Anton Lienert-Brown may edge out David Havili, and blindside flanker where splitting Akira Ioane and Ethan Blackadder is no easy task. A loose forward trio comprising Ardie Savea, Dalton Papalii and Ioane for Ireland would not surprise.
"Every loose forward has improved on this tour," Plumtree said. "All of them have got better in the areas we've asked them to and that's made selection harder. It's not like anyone has been easy to leave out. Sam Cane I thought had a really busy 80 minutes last week. Hoskins Sotutu we're happy with some of the improvements he's made. Luke Jacobson has been busy.
"If you look at Akira, Ethan, the way Ardie and Dalton have been playing all those loose forwards are putting their hands up and that's exactly what we want this time of year. Players know the competition is hot and they have to perform well.
"The team is bouncing this week I've loved the energy. We're in a rugby mad country. We know they're after our scalp and that's when the All Blacks are at their best, when we feel our backs are against the wall and we have to come out swinging so that's what we'll do."