History, it seems will always beckon for these All Blacks.

They can make more in the next four weeks - clean sweep their Northern Hemisphere tour and they will finish the season with the most remarkable record.

If they can stay unbeaten, it will be 22 tests in a row without defeat and the second perfect season of the professional age.

The first and most pertinent question is: can they keep winning? Most people have become conditioned to saying yes. Partly because of the All Blacks' form and partly because there is some kind of unconscious belief that the Northern Hemisphere sides the All Blacks will face just aren't that good.

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A few points are worth raising about the All Blacks' form. The first is that they are going to have to play the opening test of the tour - against Ireland in Chicago - without their twin towers.

Neither Sam Whitelock nor Brodie Retallick will be available. The former is a long shot to be involved at any stage of the tour while the latter was at the team hotel yesterday, in good spirits, but still not free from concussion symptoms.

He'll stay in New Zealand until he's got medical clearance. Vaea Fifita is covering for him in the meantime.

That means that Patrick Tuipulotu and Luke Romano are likely to start in the US with either Scott Barrett on the bench or one of Liam Squire, Jerome Kaino and Kieran Read asked to cover lock.

Ireland will fancy there is something in that for them to exploit but Tuipulotu is a bruising force who could be one of the big stars of this tour.

Aaron Smith will also come back in to contention - and will play in Chicago says head coach Steve Hansen.

And, with Aaron Cruden back on his feet and George Moala and Waisake Naholo also fully recovered, there is ample competition in the backs and potency with which to load the bench.

That will matter as the All Blacks can be confident they have the resources to weather injuries and fatigue.

It also means that they have some weaponry they can inject into the affray.

So far this year, the All Blacks haven't been forced to use their bench in desperation. They haven't had to roll the dice in the second half to claw back the game.

That could happen in the next four weeks.

It has been a long season already. Some players; Beauden Barrett, Dane Coles and Ben Smith, have had significant game time already.

At some stage on this tour that workload could bite, as it has in the past. The All Blacks have previously hit the wall physically at this time of year - most notably against Ireland in 2013.

They look to have the depth of talent to shuffle their resources effectively to avoid sending tired warriors in to battle.

As to whether the opposition they will face can trouble them, Hansen has no doubt they can and that the challenge of heading north at this time of year presents a host of difficulties.

"Weather-wise it is a bit different, the stadiums are a bit different and the mentality of the players we are playing is a bit different," he said.

"They will be more physical. The game up there is based on set-piece to set-piece - it is not as fluid. So we will get a good look at that on a neutral ground against Ireland in Chicago.

"They will come at us with everything they have got and bring a lot of line speed and try to be more physical. It will be a good experience for us trying to cope with it."