Dissecting the major talking points as Ireland prepare to take on the All Blacks in Dublin
Number two will face number one in the world when Ireland host New Zealand in Dublin.
Here, we examines key talking points from Saturday's mouth-watering Aviva Stadium battle.
Ireland can cope without Leavy
Flanker Dan Leavy failed a fitness test at Friday's training session, having complained of "full-body soreness", according to boss Joe Schmidt, earlier in the week. Josh van der Flier has stepped in to start in the back-row, with Jordi Murphy taking a seat on the bench.
Ireland's increasing depth is underscored by the fact that Sean O'Brien, due to his broken arm, is also missing. For Schmidt's men to boast four opensides of genuine Test quality suggests Ireland can cope with their injuries as things stand - but perhaps not too many more.
Aki must keep his cool
New Zealand have made their feelings clear in recent weeks that they do not like losing any players to rival Test nations. The All Blacks vented their frustration at ex-Hurricanes captain Brad Shields turning out for England, due to his English parents.
And assistant New Zealand coach Ian Foster this week offered a quizzical word or two about Auckland-born and raised Aki, who played Super Rugby for the Chiefs before swapping hemispheres and excelling with Connacht and Ireland, through residency qualification.
Foster said Aki "looks like an Irishman now", in a curious and hardly-disguised criticism of the 28-year-old's move north. Kieran Marmion has warned New Zealand not to bother trying to target his teak-tough Connacht team-mate however.
"It won't bother him too much, it will probably just fire him up a bit more. We expect Bundee to go straight into them, he won't hold back. He will relish the challenge, it will be a pretty good spectacle to watch to be honest."
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Schmidt a future All Blacks coach?
Win on Saturday and Ireland boss Schmidt can take a step closer to a future stint as head coach with New Zealand. The Kiwi native has plenty of hurdles to jump through for that even to be possible, granted.
But he has already guided Ireland to their maiden win over New Zealand, and doubling that victory tally would doubtless nudge him further towards the All Black picture.
Schmidt's current Ireland contract expires after next year's World Cup. He will announce his decision on whether to stay on with the IRFU or head home before the end of this year.
The smart money remains on the 53-year-old heading back to New Zealand. And a second win over his compatriots would strengthen his hand for any future employment opportunities.
Unofficial winner takes all
New Zealand will remain top of the world rankings pile whatever the result this weekend, after their 16-15 win over England. The All Blacks have now been world number one for nine years, winning the last two World Cup titles en route.
Ireland cannot topple the All Blacks on World Rugby's official rankings list this weekend then, but New Zealand boss Hansen insists Saturday's match is the true barometer of the world's best team.
That rhetoric is as much designed to motivate his own team, as to serve as a humble-brag opportunity should New Zealand pull off the victory the All Blacks always demand but tend to expect.
Any reassertion of their status as the world's best is always welcome for the All Blacks. Win on Saturday and the visitors will quietly, or perhaps not so, remind everyone of their place at the game's summit.