Touring South Africa to inspect his team's World Cup base at Pretoria University and other venues, Maradona was cheered by construction workers when he visited the huge showpiece Soccer City stadium in Johannesburg, where the opening game and final will be played.
"This is a beautiful stadium. I would love to play but my time has passed," he said.
"Today the best player in the world is Messi, without doubt, and to leave Cristiano Ronaldo second that means you have to be very, very good."
Maradona, who completed a two-month FIFA ban on Friday for making lewd comments to reporters after Argentina qualified, added: "Messi will make a great impression in this World Cup. He has what it takes and we will help him.
"I hope Messi emerges as the great player that he is and that we can all help him to the final."
Maradona dismissed fears about security at the tournament from June to July in South Africa, which has one of the world's highest rates of violent crime.
"I don't have any doubt this is going to be a great World Cup and there won't be any problems with security. (People) shouldn't be afraid of anything," he said.
