These will be strange days for his younger players and many of his older ones. This 36-34 defeat at the hands of an inspired Springboks team was the first to the old foe in New Zealand since 2009 and the first at home in the Rugby Championship full stop. The All Blacks' previous loss was in the dead rubber Bledisloe Cup test in Brisbane last October.
In romping to three bonus-point victories in this year's competition with a high-risk and often high-reward game, some among Hansen's men may have thought of themselves as invincible. Certainly, they played with an impetuosity which is often a hallmark of youth and yet they quickly discovered that if their ambition isn't matched by their skill execution then they can find themselves in trouble.
Instead, this was a case of high-risk from the All Blacks, high-reward for a Boks team seemingly incapable of finishing off the most simple of opportunities in their previous test defeats to Argentina and Australia.
Hansen won't want to blunt Jordie Barrett's attacking instincts, but he will hope the 21-year-old fullback, playing in his seventh test, takes a breath before firing another quick throw-in which could leave his side exposed. Similarly, although less problematic, Anton Lienert-Brown's intercepted pass handed the Boks the perfect start to the second half.
Game management is a lesson often painfully learned and here the All Blacks were exposed. The dropped goal question will linger too and on this Hansen is in no doubt; his men should have at least attempted the kick in the final minutes which would have won them the game.
"As I said last night, there will be a lot of learnings for us and this team hasn't had that much adversity," Hansen said. "Should we have dropped kicked the goal? Yes of course we should have; we had a lot of opportunities to but we didn't organise ourselves. It's not as if it's not something that's in our back pocket because it is.
"We helped their cause quite a bit didn't we? We threw an intercept pass, we threw a ball in … to try to throw it halfway across the field like that – Rieko [Ioane] didn't come over to help. Was it on? Well that's questionable, and that's 14 points. We helped them but to be fair to them they took every opportunity that came, they didn't miss any. That's the ball game, really.
"At one point the game could have really got away from us but with 10 minutes to go we could have won it twice. We had plenty of opportunities but we just didn't close it out. There is the biggest learning; what do we have to do when the clock's running down, the scoreboard's against us… we just have to take a big breath, do things right, and be clinical. If we'd done that we would have won the game."
These things and more will be dissected before the All Blacks' next test against Argentina in Buenos Aires a week on Saturday and then the Boks in Johannesburg a week later. One player who won't be involved in either game is flanker Liam Squire, who is out with a hand injury for three weeks.
The onus will be on Hansen to get his points across but he is good enough, and his players talented enough, and this defeat such a shock, that it shouldn't be too difficult.
Hansen was composed and gracious straight after the test and the same applied a day later and that in itself should comfort his men. His respectful tone was the right one and should be noted by some other international coaches.
"My job is to be a good teacher," he said. "Their job is to be good students. I have to be a good teacher over the next few weeks; the ball is in my court."