Beauden Barrett will drop to the bench for New Zealand's tussle with South Africa on Saturday, with Richie Mo'unga brought in at fly-half as one of four changes made by under-pressure All Blacks head coach Ian Foster.

New Zealand fell to a 26-10 defeat to the Springboks in their opening match of the Rugby Championship last weekend, recording three consecutive Test defeats for the first time since a run of five without victory in 1998.

Having also overseen a first home series defeat to Ireland, Foster has come under increasing scrutiny after the All Blacks slumped to an all-time low of fifth in the world rankings.

New Zealand have suffered five defeats in their past six Tests, but Foster vowed to fight on after the defeat to South Africa, and will rely on Mo'unga to provide creativity in Johannesburg.

Barrett was passed fit to play despite being involved in a heavy collision with Kurt-Lee Arendese in the Rugby Championship opener, but Foster has handed Mo'unga his first start of the year at number 10.

New Zealand's other changes come in the forward line, with Props Ethan de Groot and Tyrel Lomax, as well as flanker Shannon Frizell, all introduced.

There has been speculation that a defeat at Ellis Park would end Foster's thee-year tenure, but he remains upbeat.

"Belief and confidence remain high in our group, which is working incredibly hard this week," Foster said. 

"Playing at Ellis Park is always a special occasion for any All Black team, and this weekend will be no different. Adding to that, the Freedom Cup is on the line, which makes this a challenge that everyone is looking forward to."

Mo'unga insists New Zealand are shutting out criticism of their performances.

He said: "They [the supporters] care about our team and care about our results, but it's also fair of us to not care about what they think because we have a role to do, a role to play, and hearing that isn't going to help us at this moment.

"I'm at a stage now if you're not in our squad, I don't really care what you think, with all respect. We're trying our best, and we know it's not good enough for All Blacks standards."

New Zealand team: Jordie Barrett, Will Jordan, Rieko Ioane, David Havili, Caleb Clarke, Richie Mo'unga, Aaron Smith; Ethan de Groot, Samisoni Taukei'aho, Tyrel Lomax, Samuel Whitelock, Scott Barrett, Shanon Frizell, Sam Cane (captain), Ardie Savea.

Replacements: Codie Taylor, George Bower, Fletcher Newell, Tupoi Vaa'I, Akira Ioane, Finlay Christie, Beuden Barrett, Quinn Tupaea.