If the prevailing wisdom had prevailed in Chicago two years ago, Ireland would still be looking for their first ever win over New Zealand.

At the time it was said that the Kiwis would have to have an off-day AND EVERYTHING had to go right for Ireland. 

But that’s not what happened. 

Did New Zealand have an off-day? Yes. 

Did Ireland make them have an off-day or was it down to a number of factors: travel, end-of-year fatigue, lack of focus, missing a couple of handy second rows, a combination of all of those? Probably. 

Did everything go right for Ireland? Not by a long shot.

Sean O’Brien and Peter O’Mahony weren’t match-fit (said Joe Schmidt).

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Keith Earls was suspended after being sent off for Munster; Paddy Jackson, Ireland’s back-up out-half, couldn’t travel, his replacement, Joey Carbery, had no international experience.

Try-scorer Jordi Murphy injured his knee before half-time. Ireland left seven points behind off the tee.

The lesson here is that things can go wrong and it’s not game over. It’s about making fewer mistakes than your opponent and then getting a few lucky breaks along the way.

This time around the count is once again not going in Ireland's favour, however. 

The disappointment felt over O’Brien’s latest injury was cushioned by the reappearance of Dan Leavy, and the young Leinster man’s form.

But now Leavy has joined O’Brien, Conor Murray and Robbie Henshaw on the sidelines for the number two ranked team. 

Considering that Sonny Bill Williams, replaced by Ryan Crotty, is the only absentee in the visitors’ squad, and as good as Josh van der Flier is, it’s massive blow for Ireland, protecting a 10-game winning run at home in the 7pm kick-off. 

Another issue that can’t be skirted is the danger posed by the two locks that Ireland, on a run of 16 wins from their last 17 games, will encounter.

Brodie Retallick and Sam Whitelock, both of whom missed the Chicago game and returned for the 21-9 reverse two weeks later, are in situ and in ominous form.

The duo will break an All Blacks second row partnership record of 50 Tests when they line out.

The addition of Devin Toner to the forward pack is Schmidt’s answer to the stuttering lineout performance against Argentina and Ireland, who have won just once in 30 games against New Zealand, must gain parity in this area to have a chance.

It’s something Peter O’Mahony alluded to earlier in the week.

"[Devin's] a very important part of our squad. With the way the lineout went last week, it's certainly an area of repair for us," said the 29-year-old flanker. 

"Our percentages weren't where we wanted them to be."

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In a game of tight margins, the little differences matter.

Both team have a 100% scrum record from the last two games. In Chicago, Ireland had an 83.3% lineout record, New Zealand 80%.

In Dublin, Ireland improved to 90% but the visitors were flawless, 100%.

The discipline figures from the last two games also stand out.

Ireland conceded just four penalties in each game, while New Zealand were caught infringing 12 times in Chicago, 14 times in Dublin – and were considered lucky not to have more than two yellows.  

"We pride ourselves on our discipline, in training and in the game," CJ Stander told RTÉ Sport.

It would be quite an achievement if Ireland, bound to be put under massive pressure for spells, can maintain their calm and keep the figures low.

We like to make a big deal out of how Wayne Barnes treats Ireland, mostly based on the Grand Slam-threatening penalty in 2009, but if the hosts start blaming the Englishman on Saturday at nine o'clock, then they'll only have themselves to blame. 

He has has reffed them 15 times so they know what he's about. 

"We’ve been penalised a lot by him in the past, more so than any other ref, so we really need to be wary of our own discipline this week," said Sexton. 

The battle between the out-halves also promises to be special. Johnny Sexton and Beauden Barrett are both on the shortlist for World Player of the Year, and if the New Zealander gets the nod it will be a three-in-a-row.

Sexton’s kicking from hand was desperately poor in the 28-17 win over the Pumas and he knows more than anyone that it can’t be repeated.

Barrett, who won his 71st cap against England last week, has now even added dropgoals to his repertoire.

The last Aviva Test against New Zealand was infamous for the brutal manner in which New Zealand went about their business. 

Schmidt alluded to that when naming his side, which then contained just four changes, on Thursday. 

"We have got to get out there and give as good as we get," he said, for once not playing down a potentially significant deciding factor. 

"That's what is going to make it a fairly spiky sort of contest."

When Ireland are on, as they were for most of the Grand Slam campaign, they motor like an unstoppable machine. 

Against Argentina it was clear that the machine needed some oil. That's the hope for Schmidt and his men, that they have a much-improved showing in their locker. 

Rob Kearney - along with Sexton the only surviving starting back from the 40-29 2016 win - coming in will shore up the defence.

The set-pieces and kick-off receptions have to be sorted - New Zealand are the best at using restarts to retain possession - and Sexton must be pinpoint from the boot, there are a lot of things that have to go right. 

That said, New Zealand, who haven't lost in Europe since 2012, have a slight air of vulnerability. South Africa punished them in the Rugby Championship and England conspired to blow it last week in the 16-15 Twickenham loss. 

Asked about a game plan to bring down the All Blacks, former captain Tana Umaga told RTÉ Sport: "If you can keep the ball out of their hands for long periods it does frustrate them. You don't get a lot of opportunities so you've got to make sure you make the All Blacks pay." 

Also speaking to RTÉ Sport, captain Kieran Read gave a hint about how they get it right so often. 

"We know when we turn up the team against us will probably have the best game of the season and that ensures we have to get our preparation right," he said. 

The Six Nations champs could do with a few things going wrong for the back-to-back world champions, and a little bit of luck never goes astray either. 

Follow Ireland v New Zealand via our liveblog on RTÉ.ie/sport and the News Now app, watch live on RTÉ2 and the RTÉ Player or listen to live commentary on RTÉ Radio 1 this Saturday (kick-off 7pm)