The Springboks' victory over England last weekend was the first step towards national coach Heyneke Meyer's plan of world dominance.
"We really want to be the best team in the world and we need to improve every single game," Meyer said this week ahead of the second Test at Ellis Park on Saturday.
"There aren't many games left before the World Cup so we must improve in every game and it is a must-win for us."
While Meyer's nerves had settled after the Boks' first victory under his tutelage, he said he expected a backlash from the English.
"I am much more relieved, but again, in saying that, I think it is important to keep the pressure on the players," he said.
"It is important to keep our feet on the ground and be humble.
"I thought England were awesome at times and just by great defence and great discipline we kept them out.
"I don't want to get into a comfort zone where we feel now the job has been done."
The Bok mentor said his charges needed to make improvements if they wanted to clinch the series this weekend.
"They [England] will definitely come back stronger and we need to make a step up," Meyer said.
"They are a quality side and they are guys that don't give up.
"A lot of other teams would probably have let go at the end. They came right back until after the hooter."
While the challenge of facing an improved English side seemed like a daunting one, Meyer clearly relished the opportunity to test his troops.
"It is going to be an awesome battle this weekend," he said.
"That is the great thing of a three-match series because you have to be at the top of your game, every game."
Meyer said he was satisfied with certain areas of the Boks' performance in Durban, but he expected a marked improvement from both sides in the second match.
"There are a few things I am happy with, but mostly [we did not play to] our standards," said Meyer.
"We want to really improve and they will improve, so it is going to be a tough battle.
"At one stage in the second half, we really played great rugby but we didn't put the points on the board, which is unacceptable.
"They [the Boks] need to lift themselves again and we can build on that second half.
"We want to play like that for 80 minutes and that is the challenge."