If he is consigned to a six-week break, Retallick will miss the remainder of the Rugby Championship and be targeting a return for the third Bledisloe against Australia in Yokohama on October 27.
The prognosis for Ngani Laumape was more upbeat. He has a low grade strain in his knee and should be back within two or three weeks.
There won't be any need for midfield reinforcements as Ryan Crotty will be available this week and as long as an X-Ray confirms that the medics are right to believe Sonny Bill Williams has fully recovered from a shoulder injury he sustained against France back in June, then he too will be available to play South Africa.
Rieko Ioane, who damaged a hamstring in Sydney, is also back in the frame and the All Blacks, other than Retallick, are likely to unleash what most would consider to their top team against the Boks.
"There will be some changes obviously because we didn't pick our number one side last night if there is such a thing," said Hansen.
"I would imagine there will be changes. Some guys played well last night and put their hands up but it will just be a matter of when we do our selections that we have the right horses for the right courses."
As for what sort of course the Springboks represent, Hansen is in no doubt about that.
Despite the fact they slumped to a second consecutive loss against the Wallabies in Brisbane and have been well beaten in their last two visits to New Zealand, the Boks will tighten up and find a new level in Wellington.
That's always the way when they play the All Blacks – they put previous form behind them and deliver a performance that is at odds with their regular form.
There's that, and the fact that the All Blacks set out this year with the stated goal of driving their game to a higher standard.
A year out from the World Cup, they want to start embedding the gameplan to the extent that much of it flows unconsciously to enable the accuracy and intensity to increase.
There is the final incentive of knowing that a bonus point victory will seal a third consecutive Rugby Championship.
If they do, it will also be the third consecutive year they have been crowned champions with two games left to play, but Hansen was eager to play all that down and to reiterate that South Africa, with a touch of desperation about them, will demand the best out of the All Blacks.
"They will be a big challenge," he said. "They pride themselves on lifting their performance especially when they play us. They have lost two now so they will be pretty desperate and we will have to match that and be pretty desperate ourselves."