A naughty boy. Those were the three words used to describe South Africa's limited-overs captain AB de Villiers by his long-time team-mate and friend Albie Morkel. "But he has grown up now," Morkel said.

At the press conference on the eve of his debut as South Africa captain, de Villiers could well have been the excited, bouncing bundle Morkel was referring to. He bounded in, he beamed, he even bellowed out his answers. He didn't have to say it but it was obvious that he was thrilled to be there.

This has been a long time coming. de Villiers was named captain of the ODI and Twenty20 squads more than seven months ago in June 2011. He then had to wait a little over four months for a chance to lead the side for the first time, in a T20I against Australia. But the week before the match, he injured his hand during training with his IPL team Royal Challengers Bangalore and without having touched the captaincy reins himself, had to hand them over to Hashim Amla.

For those two T20Is and three ODIs against Australia, de Villiers cut a lonely figure. He lurked around the stadiums with a look on his face that said he wished he could play. He will finally get his chance on Wednesday when he walks out ahead of his team in Paarl for the first ODI against Sri Lanka.

"It's taken a while to get here," de Villiers said. "But I am really looking forward to it." Unlike Amla, the reluctant captain who stood in for de Villiers and said almost exactly the same words, de Villiers can be believed. Everything from his body language to the way he talked made it clear that de Villiers wants nothing more than to lead.

Remarkably, it is a job he has never held before. Not for a franchise, a domestic team or even at school. His main influence has been his former captain, Graeme Smith, and while de Villiers claimed to have taken pages out of Smith's book, he also insisted that he will start writing his own chapters soon.

"We are different people. I am younger and less experienced," de Villiers said. "You can expect to make a couple more mistakes. I won't be scared to try out new things and a bit of flair. I know he will be on my shoulder but he has told me that he will let me captain the way I want to."

de Villiers will also have another former captain, Johan Botha, and veteran all-rounder Jacques Kallis to lean on. The experienced hands could prove handy for him as his individual role is set to grow. Not only will de Villiers captain, he has also accepted full-time responsibility behind the stumps and may also bat at different positions in the line-up.

"It's something we have decided on for the future, it's not a short term thing," de Villiers said on his wicket-keeping role. "It opens up a spot or two in the team. Behind the stumps you have a very good view of the game, the angles and you get a very good feel about what the bowlers are trying to do."

Although de Villiers will start off batting at No. 4, he said it is a flexible position that could change at any moment. "We are going to be on our toes with that. We wouldn't like two left-handers at the crease at the same time. I might be floating a little bit. I am looking to bat at four but we are not going to be one dimensional."

de Villiers' multiple roles may seem back-breaking but apart from being fully fit after overcoming lower-back problems, de Villiers said he will relish the challenge. "Now I have a whole team to think about and I like it that way."

de Villiers wants to be at the helm of a unit who are willing to sacrifice individual goals for the good of the team and he said he had isolated one of the major improvements they need to make to be able to do that. "We have to be able to identify the situation and see when we have a situation where this is a game-breaker," he said. "Against Australia, we missed a trick here or there and we didn't attack at the right times."

The same probably applies to other instances where South Africa have tripped in the past, such as the 2011 World Cup. de Villiers acknowledged that the team had under-performed in key situations in that tournament but said they wanted to prevent that happening again. "At the World Cup, the balance of our side wasn't bad. We just didn't play well at the end."

de Villiers made that statement with none of the boyish charm and mischievous humour with which he held the rest of the press conference, confirming Morkel's statement that this boy really has grown up.

Firdose Moonda is ESPNcricinfo's South Africa correspondent