'We love playing Test matches, but we really love playing South Africa'

Ian Foster has led the All Blacks back to the top of the world rugby rankings but his focus is firmly on winning this week's milestone 100th Test against traditional rivals South Africa to clinch the Rugby Championship title.

The All Blacks supplanted the world champion Springboks as No.1 with their 36-13 win over Argentina in Brisbane hours after the South Africans had slipped to a second successive loss against the Wallabies.

The two nations will go head-to-head on Saturday in Townsville in their first of back-to-back Tests that wind up their Rugby Championship campaigns.

Having already dispatched the Wallabies and Argentina in style to boast a maximum 24 points while also rotating players, the unbeaten All Blacks can clinch the southern hemisphere crown with a game to spare unless Jacques Nienaber's Springboks can secure a bonus-point win.

"It's not on our mind at all," said coach Foster of the All Blacks' move to No.1. "I'm not saying that to downplay it."

"We'll get excited about that. We're more interested in winning a Test match than where we sit" on the rankings.

"If we focus too much on the other thing, we'll get tripped up and won't be there for very long and that doesn't interest us either.

"We love playing Test matches, but we really love playing South Africa, probably because of the amount of respect we've got for them.

"Over history it's been an outstanding rivalry. We're not so much talking about number ones and number twos, we've got a chance to go to Townsville to play a foe we've got a lot of respect for and put ourselves in a pretty nice position in this championship."

Coach Nienaber's Springboks have struggled to live up to their world champion status in the Rugby Championship and have not played the All Blacks since being beaten 23-13 by them in their opening pool match at the 2019 World Cup.

While they overcame Argentina in back-to-back Tests at home after winning a tense series against an equally conservative British and Irish Lions, limitations of their kick-first and often approach were exposed by the expansive Wallabies, made worse by uncharacteristic ill discipline and defensive lapses.

Nienaber acknowledged as much as he looks for answers to beat the all-conquering All Blacks with their many attacking options.

"It's definitely not the worst performance of the year – it's probably the worst performance since 2018 when we lost against Argentina in Mendoza," said Nienaber of Saturday's 30-17 defeat by the Wallabies.

"That is how poor this performance was.

"It's going to be a massive challenge (against New Zealand), but the nice thing is it's nice to play our Sanzaar teams," he said.

"You get tested differently and for us, it is a big eye-opener in terms of that and that is how big the challenge will be against New Zealand."