The forward was heavily criticised following his country’s failure to win the tournament but the head coach is adamant his performances were excellent.
Messi was slammed by critics and some supporters following the Albiceleste’s final defeat on penalties to host nation Chile, with the Barcelona star having scored just once during the competition.
However, the 28-year-old was named in the team of the tournament and was reported to have turned down the prize for best player, with Martino adamant his performances were of a high calibre.
“In my opinion, Messi’s Copa America performances were his best in an Argentina shirt,” he told Radio Uno.
“I shouldn’t even respond to this type of criticism, because it’s unbelievable. It wouldn’t stand up to analysis and has no basis.”
Martino was also clear that Messi has not ruled himself out of September’s clash with Mexico and says he cannot imagine the four-time Ballon d’Or winner calling time early on his international career.
“Messi has not made himself unavailable for the Mexico game. You will see that when I name my squad next week,” said the former Barcelona boss.
“As an Argentine, I would be hugely disappointed because nobody can imagine not having the best player in the world available for selection.
“No one imagines a national team without Messi.”
Martino added that he still finds it tough to look back at the reaction of his Argentina side after their loss to Chile.
The head coach said: “It hurt me a lot to see the lads’ faces after the defeat. They had prepared well.”