Messi dropped deep into midfield, particpated in five of the six goals and ended the night with three assists as the Albiceleste turned it on in Concepción on Tuesday to set up a final against Chile in Santiago on Saturday.
"If Messi gives passes that end up in goals then there is no problem," Martino said after the match. "What is more important is that he responds to what the game demands. He doesn't look worried to me. He is happy and he has no problems.
"He doesn't need to be the team's goalscorer to be happy."
"We are very happy because these guys are in another final of an important tournament in the space of less than a year," he said. "It's not the World Cup, but it's very important. We will have to work hard to win the game against Chile in the final, but today we played a good game and it's clear we were very decisive."
As well as Messi, the 52-year-old coach praised Javier Pastore after the Paris Saint-Germain midfielder scored one and was involved in several of the other goals on Tuesday.
"He played a great game," Martino said. "He was clear of his role in midfield, he showed good skills and he found the spaces to attack goal which is something we are always talking about with him."
Argentina now face Chile in Santiago on Saturday as the Albiceleste look for a first continental crown since winning the Copa América in 1993.
"We are up aganst a Chile team that are playing well," Martino said. "They have good players and have been in a process for three years. Some ideas don't change and Chile won't change against us. They will press us when they can and attack us just like they do against other teams."