"We shouldn't deify Messi any longer," Maradona said in an interview with Fox Sports. "He's Messi when he plays for Barcelona. Messi is Messi when he wears that shirt and he's another Messi with Argentina."
"He's a great player but he's not a leader. It's useless trying to make a leader out of a man who goes to the toilet 20 times before a game."
The reference was believed to be in connection with Messi's extreme nerves before games that have seen him vomit ahead of some important matches.
Messi, 31, has claimed every possible honour with Barcelona and has won the FIFA World Player of the Year award five times.
But he has struggled to reproduce the same scintillating form when wearing the blue and white shirt of Argentina.
Messi has been on the losing side in all four of his finals with Argentina – three in the Copa America and at the 2014 World Cup – and has not scored in four World Cup knockout stages.
After another disappointing tournament in Russia this year, where Argentina failed to get past the last 16, Messi opted to take a sabbatical from international football.
Maradona, who made his comments from the Mexican state of Sinaloa, where he recently took over as coach of local second-tier side Dorados, said Messi's break was a sensible one.
"I wouldn't call him up right now, but never say never. We have to take the pressure off him," he said.
Argentina beat Iraq 4-0 on Thursday with a new-look side, taking their unbeaten run since Russia to three games.
A sterner test will take place on Tuesday when they face Brazil in Saudi Arabia - without Messi.
(Reporting by Andrew Downie; Editing by Ken Ferris)
