The All Blacks back three is sure to cause the most debate around who makes the cut for World Cup selection.

It is, without doubt, the area sure to cause the most severe World Cup selection headaches for the All Blacks.

Break out the pain killers. Seven worthy contenders seem set to be cut to four in the back three.

So blessed are the All Blacks that most, if not all, could walk into any other international team at this point in time. That is not arrogance. Mere reality.

Julian Savea, Ben Smith and Nehe Milner-Skudder are thought to be certainties, leaving one spot. Waisake Naholo's swift recovery has him firmly in the picture. Charles Piutau's raw power and form in the first three tests this year was compelling. And, in a World Cup, experience then shifts towards Cory Jane and Israel Dagg, both having been there done that in 2011.

Whichever way the selectors lean debate will rage. Everyone has their personal favourites; their views on the best balance.

For former All Blacks wing Jeff Wilson, one question matters.

"My concern is if we lost Ben Smith for a couple of games who would you want out there at fullback against France in a quarter final Cardiff? That's my question and that's why, if it were me, I'd probably take Israel Dagg," Wilson said.

"That ground is soft under foot and there could be adverse conditions then all of a sudden you want a good kicking game. Dagg has got the best experience at doing that. That's why I would take him."

With Beauden Barrett and Colin Slade expected to be named as Dan Carter's deputies, the selectors may argue they already have enough fullback cover.

"I don't doubt Beauden Barrett or Colin Slade could do it," Wilson said. "It is just they haven't done it so why would you not select someone who has? I want a genuine back-up No. 15 in the squad but if they go against that I can understand why.

"It's a minefield. The good thing for the All Blacks is they could justify any of those selections. They'll have a reason for whoever they pick. This is one of the times it's not so much a gamble but about which skill set they want."

With versatility deemed valuable, another option is the All Blacks look to take a wing that can also cover fullback. This would increase the stocks of Cory Jane and Charles Piutau, who could see his move to Irish club Ulster next year count against him.

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Between Smith, Barrett, Slade and Milner-Skudder, Christian Cullen believes the All Blacks have the position he made his own covered and, therefore, favours taking Jane.

"Cory can play wing and fullback. He's got that experience and his form is on the way up," Cullen said. "Dagg is probably only just a fullback and in World Cups you need a bit of versatility.

"Especially over that part of the world in average weather in tight games you need guys like Cory Jane there. He's safe, reliable, does his job and has been there before.

"I'd go Cory Jane. Purely because I think Ben Smith is our No.1 fullback then we've got Julian and Nehe at this stage is our other wing. Flexibility outside of that is important."

One point both Wilson and Cullen agree on is taking Naholo, who will be fit for the All Blacks third World Cup match, could be an unnecessary risk, given he has only played 51-minutes of test rugby against Argentina before fracturing his leg.

"Personally if it was a Richie McCaw or one of the senior guys you'd take the risk but he's only had one taste of test rugby," Cullen said. "His time will come and that'll be next year."

Still, it would not surprise to see Steve Hansen and co take a punt on Naholo's game-breaking abilities.

Taking two halfbacks to open up an extra back three role has been considered but that path also comes with major risks.

Probable World Cup back three (test caps in brackets): Ben Smith (41), Julian Savea (35), Nehe Milner-Skudder (2), Waisake Naholo (1)

Liam Napier's World Cup back three: Ben Smith, Julian Savea, Nehe Milner-Skudder, Cory Jane (53)

Jeff Wilson's picks: Ben Smith, Julian Savea, Nehe Milner-Skudder, Israel Dagg (49)

Christian Cullen's picks: Ben Smith, Julian Savea, Nehe Milner-Skudder, Cory Jane

Also in contention: Charles Piutau (17)

Who were the All Blacks World Cup back three in 2011? Israel Dagg, Zac Guildford, Mils Muliaina, Isaia Toeava, Richard Kahui