The gateway to a third successive Rugby World Cup will run through the Northern Hemisphere, according to former All Blacks coach Sir Graham Henry.
Henry wrote in his regular column for the UK's Telegraph that he believes it will be a side from the Six Nations which will pose the most formidable threat to the New Zealanders' reign moving forward.
Meanwhile, the fading fortunes of both Australia and South Africa, who the All Blacks confront on an annual basis in the Rugby Championship, doesn't bode well for their hopes of regular elite competition against which to hone their skills.
"The greatest challenge to the All Blacks as world champions is currently coming from the northern hemisphere," Henry wrote.
"The southern hemisphere has gone backwards while the Lions have shown just what is on offer in the home unions.
The 2017 Six Nations was the best there has been for a number of years and now we have seen the challenge that the Lions have laid down for the All Blacks.
"Over the next couple of years the signs are that the All Blacks will face more competition from the northern hemisphere countries than they will experience here in the Rugby Championship. Australia and South Africa in particular have tailed off and that is a bit of a negative for the All Blacks."
However, he did make mention of the multitude of learnings the side could take from their Lions experience despite the series stalemate, ones he thinks will serve them well heading into Japan 2019.
Perhaps the All Blacks had been flattered by recent results and they simply aren't as good as they thought, suggested Henry.
"It is not that the All Blacks were complacent as to what was headed their way on this trip but it is a pretty young group and when you have won so often in recent times it is very hard not to think that you are better than you actually are, to believe that you are a little bit infallible.
"The All Blacks do not get beaten very often and it will be good for this group to experience at first hand the need to find solutions within games to what they have been presented with."
The World Cup-winning weighed in on the penalty debacle which mired the final minute of the decisive Test of the Lions series on Saturday, referring to the rule itself as "an ass" while rueing the lack of any extra time in order to determine a winner.
"As for the incident over the penalty for offside that became a scrum for accidental offside, the law is an ass.
"The penalty was given and that should have been it. As it was, the scores finished level and I would have liked to see extra-time being played.
"A draw after such a magnificent contest was an anti-climax - unlike the tour itself which has been a joyous experience for everyone here in New Zealand. We have all loved it. The next tour in 12 years' time cannot come quickly enough."
In regards to the tourists, the 71-year-old lauded their "remarkable" effort in drawing the Test series, and reserved special praise for the highly-vaunted and effective rush defensive system implemented by assistant coach Andy Farrell.
"They had chances, created openings, good openings, but they did not take them. Some of that was due to the pressure the Lions' defence put them under but it was also poor execution.
"The Lions deserve huge credit for not allowing the All Blacks to play their game. That is what the New Zealand management will be looking at going forward, how to break down the rush defence with its line speed and the umbrella format with the man in the middle pushing up.
"You have to pay tribute to Andy Farrell's defensive system, which has been as good as anything I have come across.
"It is an amazing achievement, well beyond the expectations of most people here. The backbone shown by the Lions was quite remarkable."
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