It followed a loss to Australia a week earlier in Brisbane.
"We've got to use the next seven days well, re-charge the team and make sure we finish this year on a high. We don't like having another team play at a higher intensity than us so we've got to go and figure out how to respond," he said.
Foster said the All Blacks were 'bitterly disappointed' with the result and the way they played.
The lack of Test match play had not been the anticipated disadvantage for Argentina. The time they had spent together, their two warm-up games, had seen them come into the game with 'massive energy' and a 'massive desire' to prove something for their country which had gone through a hard time.
He congratulated them on a historic result which was one of 'massive excitement' for Argentina.
"We didn't under-estimate them, we've had those sorts of arm wrestles with them before. They're a team we've got massive respect for but they've always turned a game into an arm wrestle against us and they did that," he said.
For the second week, the All Blacks had been unable to maintain their composure despite having worked on it, knowing what would be coming, he said.
"We gave them a lot of penalties and field possession, particularly in that first 40 but to their credit they looked pretty fresh, they went right through the 80 [minutes] so they've done a fantastic, and amazing job, in the last few months getting their team to that point," he said.
The All Blacks had kicked away too much ball when they had the opportunity to build phases, but Argentina were doing the same and putting the All Blacks under pressure by picking up penalties. They probably needed to do the same to Argentina.
"We weren't able to impose ourselves on them," he said.
The All Blacks hadn't taken opportunities as a result of errors, and every time that occurred, Argentina grew in belief.
Captain Sam Cane said in the first 20 minutes they hadn't had any momentum, but his message was to hang in, and their chance would come. However, compounding errors and compounding penalties had made that difficult.
Cane said despite the experience in the side, there were moments when individuals, and the team, had not shown the composure he would like to have had.
"That's a clear area of focus for us," he said.
Argentina coach Mario Ledesma said it had been a surreal experience, not because of the result, but just playing the game.
After everything Argentina had been through and was still going through, just being able to play was significant and he said, he would have said the same thing had they lost the Test.
Ledesma said there had been no magic formula to success. They had started working in January about the team they wanted and identity and culture.
"The big difference I guess is that they own it now, it's their team," he said.
The players had been outstanding throughout the pandemic, some of them hadn't seen their families for four months, and there had been no complaints.
He had already received plenty of messages from home after the win as the All Blacks were the only team Argentina hadn't beaten.
"I think we will remember this for a long time, not only because of the game but the special situation that got us to the game," he said.
Because of everything the players and management had been through it was his finest moment as a coach, he said.
Argentinians for a long time had been copying other sides, but they were different and proud of being different, and that was important.
Because they had believed in what they were doing, they were able to be disciplined in executing their game, he said.
Captain Pablo Matera said the team believed in themselves and, while there were new players in the group, they understood what wearing the jersey meant, which was seen in their performance.
"We knew we could win this game, we just had to go to the pitch and take it, No one was going to give it to us, we just went we had everything [with which] to do it," he said.