There's simply no way that all of Hansen's veterans will have the form and health to carry on to England in 2015 but deciding which ones to cut loose and when will prove a delicate balancing act.
It takes a brave coach to drop a player who has given buckets of sweat and blood for a decade but it is part of the job.
A couple of years before the last World Cup, Hansen's predecessor Sir Graham Henry laid out his winning blueprint and said he had most of his squad written on his team sheet in advance but Hansen doesn't believe he has such a luxury.
"When you look at our squad now all those same people [from 2011] are still there, so that tells us they've got a bit older and a little bit wiser and where are they at? That's one of the tough challenges we've got in our selection process over the next couple of years," Hansen said.
"So yes, there's some guys we can pencil in but probably not as many as before because there's more question marks around will they or won't they."
Those veterans that Hansen is speaking of include Tony Woodcock, Andrew Hore, Keven Mealamu, Ali Williams, Richie McCaw, Dan Carter, Ma'a Nonu and Conrad Smith.
Front-rowers Woodcock and Hore have looked off the pace with a struggling Highlanders outfit in the early stages of Super Rugby this year but Hansen said each player would be looked at individually.
Hansen also referred to Williams and Piri Weepu who played poorly for a woeful Blues side last year but were still given their opportunity in the All Blacks given what they can bring to the side.
With a three-test series against France looming in June, Hansen said making the big selection calls with an eye to the 2015 World Cup could come as early as this year.
"I think we start making them now if that's what we need to make. If the player's form is suggesting it's time then it's time. But if there's other reasons why his form's not where we need it to be then you go back to the Piri Weepu, Ali Williams [situation] - we'll support those players because we know that they can play at the highest level. They've got the mental capacity to be able to do the job that's required and it's not easy, otherwise everybody would be an All Black."
Playing the game may not be easy but Hansen's task won't be easy when he has to call some of his loyal players to inform them they're no longer required to pull on the black jersey.
Meanwhile, in other appointments, All Blacks manager Darren Shand also extended his contract with the NZRU through to the 2015 World Cup, while Dr Tony Page has been appointed to the role of All Blacks doctor, replacing Dr Deb Robinson who stepped down earlier this year after six years in the job.
