Proteas captain Faf du Plessis said Australia "definitely" made a mistake by sending an under-strength one-day international team to South Africa ahead of the Test series Down Under.
South Africa maintained their dominance over Australia after they won the second Test by a mammoth innings and 80 runs in Hobart as they took an unassailable 2-0 lead in the three-match series on Tuesday.
Australia's struggles followed their 5-0 ODI series whitewash in South Africa, where Mitchell Starc and Josh Hazlewood were rested as the tourists' and their inexperienced bowling attack struggled last month.
And Du Plessis believes South Africa's lead-in against Australia's ODI team gave his team significant confidence.
"We came across here with a lot of confidence, we did expect a really tough challenge because it's a different team and a full-strength team with two key players in Starc and Hazlewood [returning]," Du Plessis told reporters.
"Certainly, not facing them is better than facing them. The confidence from coming over five-nil has helped us a lot and I think it will be the same case going into that last Test match.
"We're a confidence team and making sure we do the basics well and if we do that we'll keep pressure on the Australian team."
South Africa showed no mercy against Australia on day four of the second Test, dismissing the hosts for 161 before lunch.
Australia had resumed at 121-2 but lost 32-8 in a stunning collapse on Tuesday as Kyle Abbott (6-77) and Kagiso Rabada (4-34) starred.
Du Plessis added: "We are a team that's confident at the moment, so we use that and we walk and talk that on the field, our body language is extremely good. But when you're a team that's under the pump and under pressure and not playing as well as you would've liked, that [confidence] fades away and it's hard to fake it.
"Even though at times they had little bits of it [momentum] we just didn't give them the opportunity to do it for long periods of time.
"Guys like David Warner and Steve Smith, if you can put a lot of pressure on them you know that the younger and the more inexperienced players in the team won't have the same punch as they would have if they back up on their [Warner and Smith's] performances.
"We've just made sure those guys have been relatively quiet in the series. Even guys like Starc, who is a fantastic bowler. He did amazing things, he bowled really well in that one spell [on day one], but that's when if you're on top you get a five-for, you clean the tail up and you bowl a team out. We were really good at making sure we stopped that."