Springbok defence coach John McFarland believes that discipline will be the deciding factor in Saturday's World Cup quarter-final against Wales.
Both sides will go into the contest in confident mood, with South Africa having hit their stride in recent pool games while Wales beat the Boks in November.
Try-scoring opportunities are likely to be rare and McFarland reckons small errors could have a huge impact, in similar fashion to Wales' narrow win over England and their try-less defeat to Australia, when the Wallabies defended their line with 13 men.
"The key to Saturday and any play-off game is your discipline with and without the ball, and you how you don't give the opposition the chance to build the scoreboard through penalties," said McFarland on Monday.
"It's essential. If you look at the England game (against Wales), the score was 28-25 with one try each, but the chance to build the score through penalties influenced the game.
"We have to improve there and be better, we don't want to give away penalties when they have the ball. We obviously want to force them to give penalties away in that situation.
"Everybody was so impressed with Australia (on Saturday), not just their goal-line defence but the way they defended the scrum and kept them out at the line-out," added McFarland.
"That's what World Cups are about."
"One thing I noticed was that Australia were far more focused, far more physical and far more content in the second-half. They put pressure on them straight from the kick-off, there was a lot of difference in the two sides at that point."
South Africa have conceded just one try – from an intercept against Scotland – in three games since their shock loss to Japan and McFarland believes they are building momentum.
"We are in a good space, we have certainly improved and we have set a marker in terms of our physicality," he explained.
"It will be a tough game on the weekend, knockout rugby always is, so it will be who works hardest, who dominates the collisions and who takes their chances.
"I think we have brought our own brand of intensity into the competition."
Wales's victory over South Africa in November prompted skipper Sam Warburton to comment that they were confident they could topple the Springboks again. But McFarland made it clear that they too rated their chances.
"We are pretty confident that we are going to beat them, so it goes both ways," said the defence coach.