Gregor Townsend says his Scotland team face their "biggest" challenge against South Africa as they seek to end another hoodoo following landmark wins against France and England earlier this year.
Scotland, who beat Australia 15-13 last week, take on the world champions in Edinburgh on Saturday as they try to end a miserable run of defeats by the Springboks dating back to 2010.
But they already have form in upsetting the odds this year, beating England at Twickenham for the first time since 1983 in the Six Nations before snatching their first victory in Paris since 1999.
A bullish Townsend said Thursday those results showed Scotland were "up there with the best teams in the world".
"When they've been given the opportunities in the last 12 months to knock over some teams they've not beaten for a while, not every time, but on a number of occasions, they've done it," he said.
The Springboks, who beat Wales 23-18 in Cardiff last week, finished third in the recent Rugby Championship, behind New Zealand and Australia.
But Townsend said they were still a major threat, pointing to a victory over the All Blacks and a Test series win against the British and Irish Lions earlier this year.
"This is the biggest challenge we've had over the last two years," said Townsend.
"It obviously makes sense when you're playing the world champions, when you play a team that is very tough to play against and has still managed to produce a win over the All Blacks and two wins over the Lions. Their form is still right up there."
Townsend said Scotland would have to dig deep to stand a chance of beating South Africa, needing to be accurate and play with "huge physicality".
"The performance in Paris and England, another one of them, but probably a little bit extra," said the former Scotland playmaker.
"Then I believe that will get us over the line but it will take an enormous effort to replicate those performances."
Townsend said Scotland had learned how to play in key periods of matches.
"It's managing the moments when maybe doubt might have crept in in the past, there's togetherness and belief that we can go and win this," he added.
"That could be on the back of a very good performance like in Paris, when we were down and we had to win or last week (against Australia) -- not such a good performance but still the drive was there to do enough to win.
"So it's more about managing the moments where you've got a chance to win and you look at your teammate and he looks confident and you go 'Right, we're going to go and win this'."