Messi has been criticised for failing to reproduce with Argentina the brilliant displays he regularly puts in for Barca but Maradona is satisfied with the 22-year-old's efforts.
"We have given him a lot of responsibility and he has done the job I have asked him," Maradona told a news conference on Thursday ahead of Saturday's friendly against Spain in Madrid.
"I am very happy with Messi," he added. "We have the best player in the world and we have to make the most of it. He has to be the boss of the team. He is in good shape and hungry."
Maradona's team were in danger of failing to reach the World Cup for the first time since 1970 during an inconsistent run of performances in South American qualifying.
The passionate Argentina coach will appear before a FIFA disciplinary committee in Zurich on Sunday over his outburst after last month's victory in a qualifier in Uruguay clinched a place at the finals in South Africa next year.
Maradona could be sidelined from matches in next year's tournament if world soccer's governing body hand down a stadium ban for his rant at the end of the 1-0 win, though he declined to comment on the hearing at Thursday's news conference.
"I am not going to talk about the issue," he said. "I will say what I have to say when I go to speak to the committee."
Addressing some of the criticism that prompted his outburst, he said: "I stopped talking to a lot of people I was talking to. In the end we decided that was for the best. The only thing I can think about right now is the national team."
