The All Blacks made 119 tackles and missed 30 – the latter a huge number by their standards.
"There have been worse All Black performances that I've been involved in but [missing] one in five is not acceptable," Hansen said in Wellington a day after the test.
"The big thing is we won't panic. Let's look at what we did achieve last night – we won a series, we played poorly and we won a series. That can't be all bad. I look at Australia and they'll be disappointed at the moment, England will be disappointed. So while we're disappointed we're still managing to do things that are positive."
Hansen felt the All Blacks were perhaps five per cent off in Wellington because they didn't possess the fear in the belly from the week before. Benjamin Fall's red card after 12 minutes would have increased their comfort levels and such are the small margins at this level the All Blacks stuttered their way to an extremely disappointing victory.
Win they did, though, something Australia couldn't manage against Ireland, with England falling again to South Africa – their fifth consecutive defeat under Eddie Jones, who described the latest in Bloemfontein as a "horror show".
Hansen admitted the selectors erred in sticking with the same match-day 23 because they under-estimated the toll the first test had taken on many of their forwards who had gone into the match under-done and they paid for it in Wellington.
He and his fellow selectors will have no choice but to go with new combinations in Dunedin due to the injuries to loose forwards Liam Squire and Vaea Fifita, both of whom are probably out with shoulder and head injuries respectively. Fellow flanker Sam Cane is due for a rest, too.
There will be an injection of inexperience, with uncapped flanker Shannon Frizell likely to be heavily involved and probably from the start.
The All Blacks will hope that brings enthusiasm and a return to the sharp edge which characterised their approach at Eden Park. If not, a French team with all players on the field at all times - something they haven't managed yet - could pose some awkward questions.