The Albiceleste captain was handed a rare place among the substitutes for the final warm-up clash in Buenos Aires but came on in the second half to double his side's lead following Ricky Alvarez's early strike.
The Barcelona star believes Alejandro Sabella's squad have built up a strong sense of trust over the past two years and says the entire 23-man party is relishing the prospect of fighting for glory in Brazil.
"I wanted to leave the bench and get on," he said after the match. "We are a very strong group, which is what we were looking for when Alejandro came in. We've built trust.
"I can see we're all excited. Now the hour of truth begins. We're going to Brazil with a lot of excitement.
"We're excited by the players we have, but we have to go bit by bit."
Argentina begin their World Cup campaign against Bosnia-Herzegovina on June 15.