Sonny Bill Williams hasn't played since injuring his shoulder against France.

Wellington (AFP) - Sonny Bill Williams’s much anticipated return to Test rugby was put on hold by tonsilitis Thursday when the ailing centre was ruled out of the All Blacks squad to face South Africa.

The All Blacks said early Thursday that Williams would start on the bench in Saturday’s Rugby Championship fixture, but he was scratched from the squad just a few hours later.

Coach Steve Hansen said Williams had been sick all week and while the plan was to play 20 minutes late in the game, there was risk he may have had to come on early as an injury replacement.

That would “flatten him”, Hansen said.

“He’s too valuable to do that to. We’ve got a good replacement in Jack (Goodhue) so in the end it was a no-brainer.”

Williams, 33, missed the first two Tests against France last June, following knee surgery. He played 58 minutes of the third Test before injuring his shoulder, and has been out of action since.

The two-time World Cup-winner’s on-again, off-again return comes as Hansen announced wholesale changes for the Springboks match.

There are 10 changes to the run-on side and five on the bench in a strong All Blacks combination looking to extend their unbeaten record in the fourth-round Rugby Championship match.

Ryan Crotty, Sam Cane and Rieko Ioane all made the starting line-up after missing last week’s Test against Argentina because of injury.

“We know that we’ll have to be at our very best,” Hansen said, noting that South Africa “will be desperate” following back-to-back losses to Argentina and Australia.

He opted for Crotty to start in the 12 jersey, with the centre confirming he was suffering no long-term effects from his sixth concussion in 15 months when knocked out playing Australia early in the series.

“It’s hard to walk down the street and not have someone ask how you are. It’s awesome that people care and genuinely hope you’re doing all right but I’m feeling fresh and good to go,” Crotty said.

Aaron Smith and Beauden Barrett are reunited in the halves while Anton Lienert-Brown will play at outside centre.

Rieko Ioane returns from injury to the left wing, while Ben Smith moves to the right wing to make way for Jordie Barrett at fullback.

In the forwards, Sam Whitelock moves into the number four jersey, with Brodie Retallick injured, and Patrick Tuipulotu comes onto the bench as lock cover for his first Test of 2018.

Liam Squire and Cane return as flankers, with the Otago Highlanders’ Liam Coltman promoted to back-up hooker ahead of Nathan Harris.

- Facing a ‘beast’ -

“We’ve had a good week’s preparation, focusing on what we need to bring to the game through our skill sets, the intensity of our play and our energy,” Hansen said.

“We’ll have to be at our very best in all these areas to counter an opposition we know will be desperate following their back-to-back losses. That means we’ll have to respond with a quality performance and a real hunger to be better.

“You just have to look at our last encounter in Cape Town to understand what kind of beast we will be facing.”

The unbeaten All Blacks lead the Rugby Championship with 15 points from three bonus-point wins.

South Africa, Argentina and Australia have one win each, with South Africa second in the table courtesy of two bonus points.

When the All Blacks last played South Africa, in Cape Town last year, they scraped home 25-24 to complete a clean sweep of the championship, after comfortably winning the first leg 57-0 in New Zealand.

New Zealand (15-1): Jordie Barrett; Ben Smith, Anton Lienert-Brown, Ryan Crotty, Rieko Ioane; Beauden Barrett, Aaron Smith; Kieran Read (capt), Sam Cane, Liam Squire; Scott Barrett, Sam Whitelock; Owen Franks, Codie Taylor, Karl Tu’inukuafe.

Replacements: Liam Coltman, Tim Perry, Ofa Tu’ungafasi, Patrick Tuipulotu, Ardie Savea, TJ Perenara, Jack Goodhue, Damian McKenzie