Another loss would draw further ire from fans and New Zealand Rugby administrators and even a victory might not be enough to save his skin.
Adding to the drama, the test is at the Springboks' spiritual home of Ellis Park, where winning is considered one of the toughest challenges in world rugby.
All Blacks captain Sam Cane said they were "desperate to improve".
"We have taken a good look at the missed opportunities and where we can get better. We were brutally honest with each other. It was never personal. It's about learning from an individual's mistake so that the team can improve."
The All Blacks have lost three tests on the trot and were thoroughly outplayed in last week's 26-10 defeat in Mbombela, their biggest defeat to the Boks in almost 100 years.
Despite the bombardment of criticism Foster is adamant the team is on the up and he has made just four changes to his starting XV for Sunday's second test in Johannesburg, with Richie Mo'unga replacing Beauden Barrett at first-five, and props Tyrel Lomax and Ethan de Groot and loose forward Shannon Frizell coming into the run on side.
Despite staring down the barrel of a sixth defeat in seven games, the beleaguered coach remained positive.
"Everyone keeps putting those stats up. We're not in that space," Foster said.
"When you look at the championship, we've dropped the first one. There's no good lingering on the past. We know we've got some development [to do] as a team, and the growth is always hurting. At the same time, our goal is to improve, improve, improve, and doing it at Ellis Park is going to be cool."
While a loss could spell the end of coach Foster's reign, Cane's position as skipper would also come under further scrutiny.
He dismissed suggestions the All Blacks were at the point of having "nothing to lose".
"There is a trophy on the line, we are playing at Ellis Park and we are desperate to improve and put up better performances than we are, so there is as much on the line as there has ever been."
First-five Richie Mo'unga understands why All Blacks supporters have been disappointed and even angry with their recent results.
While he respected the right of fans to vent their frustrations, Mo'unga said the team must ignore the 'outside noise'.
"It's very fair. A team they support that usually gets results is not getting results, and it's fair the fans care.
"They care about our team and care about our results, but it's also fair of us to not worry too much about what they think, because we have a job to do and hearing that isn't going to help us at the moment."
The All Blacks cannot afford to be distracted as they try to beat the odds and win at Ellis Park, with the TAB paying $2.70 for a New Zealand win - the biggest opening price the All Blacks have been in the professional era.