The Barcelona star made the shock announcement after his nation's loss to Chile in the Copa America Centenario final in June.
But, just months later, Messi said he would continue playing for Argentina, a decision that Martino – who resigned in July – expected.
"I knew Leo would rethink the idea of retirement," he told ESPN FC.
"I was convinced the decision to leave the team was after different issues."
Martino's first job post-Argentina will be with Atlanta United after he was named coach of the MLS expansion side.