The 29-year-old has already scored five goals and added a further four assists in this year's tournament, despite playing just 254 minutes thus far.
With Argentina preparing for a final meeting against Chile in the early hours of Monday morning, Martino believes that Messi - now La Albiceleste's all-time leading scorer - has once again shown that he can replicate his club form with Barcelona on the international stage.
"He's really found a very similar form as in Barcelona," ESPN quotes him as saying. "He's been playing with the same people for a long time - that makes him feel very good, very happy.
"Really, I think for a long time now, he's been performing well for the national team. He's had many more positive performances than not-so-good performances.
"He's in a good place. The way he's been in Brazil, the way he was last year and the way he is once more now. He's the face of the team. And really he's a reflection of the commitment of all of us to win tomorrow's match."
Messi won the Golden Ball award at the 2014 World Cup as the tournament's best player, but could not help Argentina overcome Germany in the final.