That meant adapting some structures for Sunday's encounter in Buenos Aires to ward off predictability.
Players have also repeatedly spoken of the need to dominate the encounter early and silence a raucous Argentinian home crowd.
"I guess you can talk about their 50 minutes, and we did pretty well in that last 30 but we've got to be careful," Foster said.
"They would've learned a lot about us in that last 30."
The All Blacks have traditionally eschewed frequent squad changes under coach Steve Hansen.
But Foster felt he and his fellow coaches had learned in previous tours that some changes were necessary to keep energy levels high.
All players were training well in the lead-up to Sunday's match.
Either Elliot Dixon or Liam Squire will fill in for the crocked Jerome Kaino at blindside, while others including prop Wyatt Crockett could start.
However Foster said squad changes, if made, would not be wholesale.
"If we are putting newer players in there, then they've got players around them who can enable them to just go out there and do what they need to," he said.
Crockett, 33, said he and his fellow front row teammates had been training hard in the hope of overcoming the Pumas' renowned physicality.
"There's a pretty good threat, you could be embarrassed scrumming Argentina," the Crusaders veteran said.
The 52-cap Crockett, who made his test debut in 2009, also expressed his wish to play through to the 2019 World Cup in Japan.
