A two-time World Cup victor, his chances of adding a third appeared over when he left for France.
New Zealand All Blacks' Damian McKenzie celebrates his try with Argentina Puma's TJ Perenara in the second half in New Plymouth, New Zealand, September 9, 2017.
Their prolific and versatile fullback Damian McKenzie has been ruled out for the tournament in Japan later this year after confirmation he's ruptured his anterior cruciate ligament.
"There are some guys who aren't here that, if you were picking it on form, probably would be here, but the rules are the rules and we are all playing by them".
Hanson said he was impressed with the veteran centre's form this season.
"He's just been Ma'a, hasn't he?" Hansen said. "You get the subtle touches and you get the brutality, as ALB [Lienert-Brown] found out at the weekend".
"What is important is he comes back when he is ready and he is confident", Hansen said.
"I just like the fact that he has been courageous enough to come back, and he will be considered like anybody else".
"We know he can play test rugby, he just has to show that he's got the ability to do that on a weekly basis at Super Rugby level and then we have to make hard decisions".
The 23-year-old damaged his right knee when attempting a tackle on Blues flyhalf Otere Black in Hamilton last Saturday.
New Zealand will open their title defence against South Africa in Yokohama on September 21.
The utility back joins at least nine other All Blacks on an injury list headed by Sonny Bill Williams and Owen Franks.
"He could be out for eight to nine months", Hansen told reporters.