Not for the first time this summer, South Africa have the opportunity to close out a series against top-quality opposition but unlike the other two occasions, they only have one shot at it. After taking the series lead against England in the ODI and T20I rubbers earlier this month, South Africa went on to lose the fixtures that followed (the second ODI against England was rained out) and were denied the chance to claim a trophy outright.

Wednesday's T20I against Australia presents an opportunity to change that and for the new coaching regime under Mark Boucher to earn their first cup, and although they see results as secondary at this stage, the team's assistant coach Enoch Nkwe did find reason to say, "We're going to take it like a knock-out game or a World Cup final."

That important.

Boucher and his team were hired with the next 50-over World Cup as the end goal, which may make the two T20I tournaments in-between seem incidental, but they are very much part of the plan. Whether South Africa can seriously think of the winning this year's event may not become clear until later, when they put the final touches to their squad and their form becomes apparent.

For now, Nkwe said they are focused "finding the formula" by experimenting with combinations and working through inconsistencies. "By the time we get to West Indies [in July-August], it's important that we've formed something special as a unit and we understand each other's game and what makes us tick."

South Africa already know that Quinton de Kock has embraced the extra responsibility of being a leader. He has scored two fifties since being named permanent captain in T20I cricket, and also has two more from when he stood in for Faf du Plessis in India last September. They also know the batsman most likely to open with him, Temba Bavuma, but that will have to wait until he has recovered from a hamstring injury. The rest of the line-up is much less certain with positions from No. 3 to No. 6 up for grabs.

Du Plessis, Rassie van der Dussen, Jon-Jon Smuts, Heinrich Klaasen, David Miller and Pite van Biljon are the six players currently competing for four positions.

Du Plessis sits on top of that pecking order, considering he is South Africa's fourth-highest run-getter in T20Is and brings a skill-set they simply can't do without in this time of transition. "He is blending in nicely," Nkwe said. "It's never going to be easy from being in that [captaincy] position, giving it up and trying to find where you fit in. We have given him a different leadership role to assist Quinton and you saw in Port Elizabeth they worked on together tactically. We need that experience. We can't throw it away."

Van der Dussen is not far off becoming a mainstay either, having emerged as a cool head and a clean-hitter, but there is stiff competition among the rest.

Smuts offers a bowling option with his left-arm spin, Klaasen is an aggressive strokemaker who can win matches on his own and van Biljon has not had enough of an opportunity to show what he can do yet, which adds to the pressure on Miller to step-up. Miller is still seen as a player with potential than a proven match-winner, which is what he needs to be now that he has been in international cricket for a decade. When Nkwe was asked if Miller's experience guarantees him a place in the T20 World Cup, he answered, "I don't think anyone is certain."

South Africa have to walk a tightrope at the other end as well because, unless Smuts plays, the make-up of their XI only gives them five bowling options (as was the case in Port Elizabeth). Dwaine Pretorius and Andile Phehlukwayo are competing for the allrounder's spot with the frontline pace attack made up of three out of Lungi Ngidi, Kagiso Rabada, Anrich Nortje and Dale Steyn.

Rabada's role is particularly important after he was given an extended period of rest for the England series, then returned with 0 for 45 in three overs at the Wanderers, before tightening up in Port Elizabeth. Nkwe believes Rabada still has room for improvement. "I feel there is a lot more. He feels the same," he said. "He is working hard. He is about 60-70% to his best. Hopefully tomorrow he manages to give himself the best chance to be as close as possible to his best but sometimes it does take a while to get going."

The same can be said of South Africa but Boucher and co will hope that some of the kinks have been ironed out just enough that they can savour a first series win on Wednesday.

Firdose Moonda is ESPNcricinfo's South Africa correspondent