McCaw suffered what coach Steve Hansen thought was a torn medial ligament in his left knee after Charlie Faumuina had fallen on the flanker’s leg in a tackle.
“It looks like he’s done a medial. How bad? It’s not grade one, it will be a two, three or four,” said Hansen following a match played at a rain-lashed Waikato Stadium.
Hansen said later that McCaw was likely to be out of action for up to five weeks, ensuring he will miss the remainder of the four-nation tournament.
The Pumas opened the scoring with Juan Manuel Leguizamon’s try which Nicolas Sanchez converted.
But the All Blacks seized control and Carter, who had started on 1,399 points, slotting a penalty before Aaron Smith scored two quick tries.
Sanchez added a penalty to reduce the gap, then Carter and Sanchez traded early second-half penalties before the All Blacks’ Julian Savea went over. Carter converted to give the home side a 25-13 lead and was then immediately replaced by Barrett, who slotted a late penalty.