Messi has been brilliant for Barcelona but struggled to make an impact for Argentina, sparking criticism of his performances and Maradona's failure to make the 22-year-old fit in.
"If I had to change for his good, I'd change," Maradona told local radio station Cooperativa.
"But I think that with the system we have and the players we have all he needs is to explode, and surely he will do that at the World Cup."
After his return from a tour of Europe to see his leading players, Maradona said he had "the most emotional conversation" with Messi since he met him.
"I saw a Messi totally convinced of what he wants. We believe in him to the death," said Maradona.
"He's not Lio any more, he's Messi. He has rights he's earned on the pitch and he'll have to make his leadership felt on it."
Messi scored hat-tricks in successive La Liga games recently and is earning comparisons with some of the greatest players to play the game, including Maradona.
"If anyone surpasses me I want him to be Argentine. If Messi does well, I win," said Maradona.
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