Sonny Bill Williams will play his 50th test for the All Blacks this weekend.

Sonny Bill Williams will play his 50th test for the All Blacks against Australia on Saturday, eight years after his international debut.

Injuries have limited the midfielder's game time this year, both with the Blues and with the All Blacks, but he's over those now, and looking to cement a place in Steve Hansen's plans, one year out from the World Cup.

With the milestone of 50 caps now in sight, Williams revealed it had seemed an unlikely number when he started his international career back in 2010.

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"I think it ended up being a goal," Williams said on Thursday.

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GETTY IMAGES Sonny Bill Williams says he is wiser now he's older.

"At the start I don't think it was realistic, but I'm just grateful and blessed to be in this environment, rubbing shoulders with some of the best players in the world. It's been a really blessed journey and I'm just grateful to still be here."

It's been a decade since Williams first switched from league to rugby, leaving the Bulldogs in the NRL to join Toulon in France. He said he found it easier to deal with injury setbacks, given the length of time he has been playing.

"I guess a little bit of wisdom does come with age but you have to go through those calamities and struggles, so I'm no different. When you do go through those things you can fall back onto what works.

"I like to say your reality starts with your mindset. That's what I've been focusing on."

Williams has only played eight games of rugby in 2018 - five with the Blues and three with the All Blacks - but he is confident he is ready for what lies ahead, with tests against England and Ireland to follow after Saturday.

"My feet are firmly on the ground right here and I know I've got to make every day a winner," Williams said.

"I haven't had many minutes playing rugby this year but that's what I need. I've got confidence in my ability that once I get those minutes I'll be world class, so I don't have any doubts there."