A weak performance could be severely punished by Jake White's Springboks.
However, another victory, after the 31-21 win against Ireland a fortnight ago, will send Scottish expectations for the World Cup soaring.
Webster said: "What has been talked about by the Scottish management team is that in these warm-up games we're trying to build momentum and create a winning feeling - so there is a massive desire to do that at the weekend.
"We've made steps forward from this time last year, and I guess on Saturday we'll be able to see how far we've come."
The Edinburgh star was at the centre of the action when two controversial refereeing decisions had a crucial role in deciding the outcome of the second Test during Scotland's tour of South Africa last summer.
He was first denied a try on the stroke of half-time when referee Tony Spreadbury ruled the ball had been knocked on following a scintillating break.
Then, in the second half, Chris Paterson scored from an interception only to be called back because Spreadbury had spotted a Webster knock-on earlier in the move.
The Springboks ended up scoring from the resulting scrum, meaning that decision alone had led to a 14-point swing in the home team's favour.
South Africa ended up winning the match 29-15, and clinching the series 2-0.
Webster said: "Whenever you lose a game it is obviously disappointing, so it was heart-wrenching to be on the wrong end of that 14-point swing - but that was then, this is now."
The 26-year-old played the full match against Ireland earlier this month and welcomes the strong opposition for Scotland.
He also expects South Africa to be wary of his talent, and if not intends to show what he can do.
"Being a winger I see myself as more of an attacking threat than maybe some of the forwards," Webster added.
"So if a team was looking at Scotland or any other team I was playing in and thought that I wasn't worth a mention then I would be pretty disappointed with that.
"I'd like to think that teams should be saying that this guy is slightly dangerous."