A murky picture just got murkier with All Black coach Steve Hansen floating the idea that it's possible they could take only three locks to the World Cup.

Gauging whether that option sits on the probable or improbable end of the spectrum is difficult and perhaps even the selectors don't know how they feel until they see how tomorrow night plays out.

They are taking the Wallabies on without a specialist lock on the bench, backing Jerome Kaino to be capable of slipping into the boilerhouse if needs be.

All Blacks head coach Steve Hansen explains why Victor Vito has been selected and how that affects how many tight forwards as locks may travel to the Rugby World Cup.

Kaino has been asked to do this before - as recently as last year at Ellis Park. A concussion ruled out Brodie Retallick for that test and there wasn't time to fly a specialist over. So Kaino, who started, and Steven Luatua from the bench were the locking cover options. The latter nailed his aerial work but didn't provide the scrummaging ballast; Kaino ticked both boxes, which has encouraged Hansen to have another look at that at Eden Park.

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"Is this something we can do, carry against certain teams a loose forward who can play lock?" Hansen said. "There is no question JK [Jerome Kaino] has scrummaging ability. He is a very good scrummager at lock. He's done a bit of it with us and in a previous life, other teams.

"We just feel for us it gives us more options. It might, for example, allow us to take an extra loose forward to the World Cup as opposed to taking four locks, for example."

All Blacks head coach Steve Hansen fronted the Bledisloe media today and knows the All Blacks have to play their own game to win the Bledisloe Cup.

Kaino doesn't necessarily strike one as a natural lock-cum-loose forward, but if he can provide more evidence on Saturday that he can slug it out in the role for 20 minutes or so, it may indeed become a tempting option to travel to England with just three specialist locks.

Two other factors may sway their thinking in this regard. The first is that the breakdown and tackled ball area are having an ever greater influence in determining the outcome of tests.

If Kaino can genuinely cover lock without weakening either the scrum or lineout, then the All Blacks can put two loose forwards on the bench for certain games at the World Cup. That will be a tempting option to have up the sleeve - to be able to have four loose forwards on the field in the closing stages of big games. Having the ball and keeping the ball will be critical and ball carriers and breakdown experts may be more valuable that tall timber.

If you ask the All Blacks players and the head coach Steve Hansen who is perhaps the world's greatest player (if not the modern era) the name cried out is Richie McCaw.

There's also the reality that neither Jeremy Thrush nor James Broadhurst are proven, crunchy, big test performers. The All Blacks are likely to rotate Retallick, Sam Whitelock and Luke Romano at the World Cup and it would be questionable how much a fourth lock - probably Thrush - would actually be involved.

Potentially the All Blacks could get by with just three specialists and take seven loose forwards instead of six. That would pave the way for both Liam Messam and Victor Vito to go. Having a relatively soft pool means the All Blacks could cover any short-term injury to one of the specialist locks with Kaino, while for any serious injury they would have to send for a permanent replacement anyway.

Going to England with just three locks is possible, maybe even probable after Saturday night.