South Africa captain Siya Kolisi is targeting a more consistent run of results for the Springboks as uneven form has left the outcome of this year's Rugby Championship hanging in the balance with two rounds of matches remaining.

The reigning world champions picked up their second win of the campaign against Australia in Sydney on Saturday to leave them in third place and one point behind first-place New Zealand as the four-nation competition reaches its climax.

"The thing is everybody wants consistency," Kolisi said. "We want to stay near the top the whole time but it's hard."

"Some teams perform one week and some teams don't perform. That's what I think all the nations are looking for, that consistency every week.

"You can see now what's happening, every single team is standing up and I think it's brilliant for rugby because you never know which team is going to win on the day."

Any of the four nations in the Rugby Championship can still claim the title with no team able to dominate this year's campaign. Each has two victories and two defeats, but New Zealand leads by virtue of Saturday's bonus-point win over Argentina.

Two early tries put the South Africans in control against Australia in Sydney, a week after allowing the Wallabies to open up an unassailable advantage before several late scores narrowed the margin of defeat in Adelaide.

"Last week there was nothing different to our performance or our game plan, we took the opportunities that we created today and that's what we want to do each and every single time," Kolisi said.

"It will make our job so much easier, not to have to fight back the whole time.

"The fact that we could create those opportunities is encouraging, and the fact we could finish today was really good for us as a team, and it's a good reminder that we can do it going forward.

"We must just keep on doing them, that's all we want. Just being consistent and taking the opportunities when we create them."

South Africa will face Argentina in its last two games in the competition later this month while defending champion New Zealand will play Australia.