Lock Scott Barrett could miss the start of the World Cup after becoming only the fourth New Zealand global to be sent off during a test match in the 47-26 Rugby Championship loss to Australia in Perth.
"When they're got 15 on the field it feels like 20, so when they've got 14 on the field it still feels like they've got 17 or 18", he said.
While the Kiwis lifted, the Wallabies selections backfired.
The new selection panel must take some credit for the turnaround, with director of rugby Scott Johnson and dual global Michael O'Connor joining coach Michael Cheika.
"I'm disappointed but Australia deserved the win as they were the best side on the day", Hansen said.
"Everyone has got a piece in the Ferris wheel to make it go round, so you can't just turn round and say the players didn't do it, everyone is responsible and don't have any problem taking that responsibility that's why you put your hand up to coach".
"But it is half the job done, and we know they will come out firing next week".
The match was also notable for Scott Barrett becoming the fourth All Black to be sent off in a test match after a receiving a red card just before halftime.
On top of that, their new back-row combination failed to fire as they started two regular openside flankers in Ardie Savea and Sam Cane alongside skipper Kieran Read, trying Savea at No.8 with Read switched to blindside.
"All Blacks thrashed", "Bledisloe Bashing", "Wallabies shock All Blacks", "Hansen has "egg all over face", screamed the headlines while Radio New Zealand, perhaps unable to face the truth, posted the headline "All Blacks beat Wallabies" on their webpage before giving the correct match details.
"Those great All Black World Cup loose forwards of not long ago, McCaw and Jerome Kaino, didn't bother with pointless cheap shots, an attitude which worked".
Despite the euphoric post-victory scenes, the most anxious rugby fans remained fearful the All Blacks had run dead; that their eyes were on the much bigger prize at the World Cup and they were easy pickings.
"A few things went our way but I was really pleased for the lads", Cheika said.
"We were starting to get into the game and then, lack of discipline, we get a guy sent off and it's not a team you want to play with 14 against".
He said the Wallabies must improve, just as the home side would.