All Blacks coach Steve Hansen says Sonny Bill Williams has matured from the player who once would sulk over injury setbacks.
The big midfield back ends three months of recovery from a shoulder injury when New Zealand face Argentina in Saturday's Rugby Championship Test in Buenos Aires.
While Hansen made a number of surprise selections in a team seeking to bounce back from their home loss to South Africa, it was widely expected veteran Williams would return at inside centre.
The 33-year-old has been sidelined by injury several times this year, the latest being damage to an AC joint suffered against France in June which has taken longer than expected to heal.
Williams was poised to return but missed the stunning 36-34 loss to the Springboks two weeks ago in Wellington with tonsillitis.
It's something which Hansen revealed would have sent the former NRL star to a dark place earlier in his career.
"Once upon a time he would have sulked a lot about being injured and not getting games, but he has matured into a really good human being," Hansen said.
"He understands there is no point being down about it, so he is pretty positive. He is a positive person around the environment whilst he is injured, he just gets on with his trainings.
"He is fit, probably as fit as I have seen him - running fit I am talking about."
Williams' leadership will be important against the improved Pumas in a New Zealand team shorn of experience.
Hansen was critical of a lack of quality decision-making late in the Springboks defeat, yet has chosen to demote a number of his more accomplished players in making six starting changes.
Captain Kieran Read will join the tourists in Pretoria to face South Africa to ease the travel load on his back while centurion prop Owen Franks is surprisingly rested, leaving raw combinations in the front row and loose forwards.
Hansen also had an eyebrow-raising reason for starting usual reserve halfback TJ Perenara ahead of Aaron Smith.
Perenara will play his 50th Test.
"He deserves to have the No.9 on his back when he goes out to play that," Hansen said.
"He is a big part of who we are and is one of our leaders. If it was the other way around and 'Nuggie' (Smith) was playing his 50th, he would probably be starting."
