Argentina captain Messi was coy over his future during an interview with newspaper Ole in his homeland this week, stating his desire to remain at Barca before adding cryptically that "things don't always work out as you want them to".
Messi agreed a new contract earlier this year and had been expected to stay at the Camp Nou until retirement.
And Martino, who now coaches Messi at international level, believes the four-time world player of the year is unlikely to move.
"When you see the connection he has with Barca I think it would be very difficult for him to leave the club," he said after Argentina's 1-0 friendly defeat to Portugal on Tuesday.
"However, when you see the options out there in the world, the big teams where he would fit in perfectly, then I think it’s possible.
"But I definitely think he should be happy where he plays his football.
"I've never spoken to him about the issue and everyone does what is best for themselves."