Mo'unga keeps All Blacks flyhalf jersey for Springboks opener

The reigning World Champion All Blacks haven't always had it their way (3:33)

New Zealand are the most successful nation in Rugby World Cup history, but it wasn't always so. (3:33)

Beauden Barrett will start at fullback for New Zealand in their World Cup Pool B opener against South Africa in Yokohama on Saturday after coach Steve Hansen retained Richie Mo'unga at flyhalf.

Barrett has played most of his career at flyhalf but has been shifted to fullback this year in order to accommodate Mo'unga, though he did start the All Blacks' final 92-7 warmup win over Tonga in the number 10 jersey.

Hansen has often trumpeted the quality of his extended squad and the ability of players to adapt.

For Barrett, that means facing a likely barrage of high balls against a South African side eager to pressure an All Blacks' back three which includes inexperienced wingers George Bridge and Sevu Reece, who have only eight caps between them.

"Any combination of players in our squad could have justified their selection. But in the end we believe the 23 we have selected is the right group for this opposition," Hansen said.

The world champions are without lock Brodie Retallick, who was injured in the 16-16 Rugby Championship draw with the Springboks in July. Sam Whitelock and Scott Barrett make up the second row pairing.

Scott Barrett on Saturday will face Jerome Garces again, the referee who sent him off in the recent 47-26 loss to Australia in Perth.

Ardie Savea will wear the number six jersey, with Sam Cane and captain Kieran Read the other loose forwards.

Ryan Crotty and Anton Lienert-Brown are the centre pairing, with Sonny Bill Williams on the bench.

"In today's rugby environment, you need to have the mindset that it's not just about who starts, it's also about what the players coming off the bench can provide," said Hansen.

"As an example, we have a great one-two punch with Dane (Coles) and Codie (Taylor) at hooker and Aaron (Smith) and TJ (Perenara) at halfback.

"To perform at our very best, we'll have to play with real clarity, intent, energy and clear heads. Both teams will have their moments and it'll be our job to ensure we limit theirs and take full opportunity of ours."

New Zealand: Beauden Barrett, Sevu Reece, Anton Lienert-Brown, Ryan Crotty, George Bridge, Richie Mo'unga, Aaron Smith, Kieran Read (c), Sam Cane, Ardie Savea, Scott Barrett, Sam Whitelock, Nepu Laulala, Dane Coles, Joe Moody, Replacements: Codie Taylor, Ofa Tuungafasi, Angus Ta'avao, Patrick Tuipulotu, Shannon Frizell, TJ Perenara, Sonny Bill Williams, Ben Smith.