Damian McKenzie ruled out of Rugby World Cup with knee injury

Damian Mc Kenzie leaves the field.
Chiefs v Blues Super Rugby FMG Waikato Stadium

Damian Mc Kenzie leaves the field. Chiefs v Blues Super Rugby FMG Waikato Stadium

"'He's done an ACL and looks to be out for eight to nine months which is a real shame for him", Hansen said.

Hansen described Nonu's return to the Blues and goal of making another World Cup four years after his last test as "brave" and said the selectors would have some hard decisions to make around the make-up of the midfield if the veteran's good form continued.

"There are some guys that aren't here, that if you were picking on form probably would be here".

Steve Hansen has been as impressed as anyone at Ma'a Nonu's form on his return to New Zealand rugby with the Blues, and says a place in the World Cup squad is possible for the 36-year-old.

Nonu on the charge for the Blues against the Chiefs.

He was picked as one of the 41 players to attend today's All Blacks foundation day in Wellington, and was highly likely to be one of the three first-fives selected for the World Cup, along with Beauden Barrett and Richie Mo'unga.

He returned to New Zealand late past year and signed with the Blues.

"He's just been Ma'a, hasn't he?" You're getting the subtle touches and you're getting the brutality.

Nonu burrows over for a try in the Blues' loss to the Chiefs.

"None of us knew what Ma'a was going to come back like", Hansen said.

Sonny Bill Williams and Nonu at the 2015 Rugby World Cup.

"I just like the fact that he has been courageous enough to come back, and he will be considered like anybody else".

"We've got to expect injuries and there'll be more than just him, I suggest, by the time we finally name the team to go to the World Cup", Hansen said. "As someone pointed out, there are a lot of good players in that position so there will be good people who miss out".

He was dropped for the 2007 Rugby World Cup, but returned to become an All Blacks regular from 2008 until his departure for France.

He said the midfield was an area where there would be plenty of competition, but Nonu was staking his claim strongly.

The Wellington-born former Hurricanes stalwart was one of the All Blacks' best performers in the 2015 title-winning campaign.