After the series loss to Ireland, Foster was aware of the demand from the rugby public that the All Blacks respond.
South Africa would be tough to crack, he said.
"They're tough, they're physical, they've got some areas of their game they are focused on, particularly around the mauling game, the driving game, and that's an area that hurt us in that third Test, so we've got some clear areas we've got to improve," he said.
Foster said since the 2-1 series loss to Ireland, there had been a week of robust discussions with the team's management, New Zealand Rugby, and senior All Blacks.
Those discussions were something that should happen.
He was proud of the accountability shown by each cohort, and the All Blacks had a clear plan, with utter commitment, of how they would move forward.
"We are never happy when we don't achieve what we want to," he said.
"We understand the fans aren't happy with that, but you have a promise that we are looking forward to getting stuck into our work," he said.
They would come together next week for a camp before heading to South Africa with a goal of playing a quality of rugby New Zealanders could be proud of.
Foster said there would be some changes in the future. They were being worked on, and he couldn't comment further.
He said he was strong, resilient, and felt he had a great feel for, and relationship with, his players. He was strategic and also accountable.
"There's no doubt I'm under pressure, but can I also say, I'm always under pressure. I've always felt that pressure.
"External people will try to intensify that pressure, but it doesn't change the fact that, as an All Blacks coach, you live in that world all the time," he said.
It was his job to ensure, through robust processes, that the right people were sitting in the right seats.
Foster said he believed in captain Sam Cane both as a leader and person.
Joe Schmidt's role with the side was as an independent selector replacing Grant Fox with a secondary role of opposition analysis and working with Foster on the strategic area in which the team needed to move. He would not be travelling with the team.
Regarding the changes in the squad, he said he was delighted with prop Ethan de Groot coming in and having done what was asked of him over the last six or seven weeks.
"[He's] A lot leaner, a lot fitter and excited with his selection. Also pleased to welcome back Shannon Frizell who, again, has a lot of experience, but interruptions the last 18 months, but really feel he's in a good spot to come back in," he said.
Some extra players would cover what he called 'a reasonably significant injury list'. Hurricanes' prop Tyrell Lomax, Highlanders' lock Josh Dickson (for more of a longer term arrangement due to Brodie Retallick's broken cheek bone) and centre Braydon Ennor to cover Jack Goodhue's injured knee.