Sydney showdown for world No.1 ranking

The series may be decided but there is still a huge incentive for Australia – apart from the pride of playing for your country – come Sunday's fifth and final Carlton Mid ODI at the SCG.

A century from Steve Smith and some late-order power hitting from James Faulkner gave the Melbourne crowd a treat and lifted Australia to a three-wicket win over South Africa on Friday night.

The victory gave the hosts an unassailable 3-1 lead in the five-game series.

But Smith says his side won't be short of motivation in Sydney, and said he hoped the fans would flock to the SCG where another win would ensure Australia reclaim No.1 spot on the International Cricket Council's ODI rankings.

"It adds a lot," Smith said.

"We pride ourselves on that. We try to get to No.1 in every form of the game.

"To win in Sydney would be great and to take that No.1 mantle back would be outstanding."

Smith added that Australia's one-day form augurs well for the World Cup, especially given the quality of the opposition.

"South Africa are a very good line-up," he said.

"To play the way we have and beat them 3-1, it's been very satisfying for us.

"It will be perfect to finish it off with a 4-1 victory and take back that No.1 spot.

"It's going to be nice playing the World Cup in our own backyard ... hopefully, that (form) continues going into the World Cup."

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South African coach Russell Domingo suggested Smith's scalp would be key to his side ending their limited-overs tour of Australia with a win.

"He's obviously a big player for Australia at the moment and we've got to make sure our plans are in place when we play against him," Domingo said.

Proteas captain AB de Villiers looked in great pain in the final stages of Australia's innings on Friday and Domingo confirmed it wasn't caused by Smith and James Faulkner's batting.

"He just fell badly on his rib and I think he took a blow there in one of the games earlier in the series," Domingo said.

"Maybe just a bit of bad bruising. I think he should be ok (for Sunday)."

Domingo denied his side's first one-day loss to Australia at the MCG was a World Cup setback, and said Sunday would be a chance for his charges to nail down a spot in the squad for that tournament.

"Sunday is another chance to see what the right group is ... we're pretty close to finalising (a squad)."