Parreira said it was imperative that the host nation won the match to avoid needing a result in their last group game match against France next week.
"We have to be decisive and go for it. There will be no sitting back waiting for (the other team's) mistakes. We have to take risks, otherwise we'll be going nowhere," he warned his players on Tuesday.
"If we get just three draws we'll get knocked out of the tournament. I prefer to take the risk to give us a better chance of going to the next round.
"We need to win, we don't want to go to the final game needing to win," Parreira told the pre-match news conference in Pretoria.
NOT CONFIRM
The coach said he would make one, maybe two, changes to the side that started Friday's opening World Cup match against Mexico
Leftback Tsepo Masilela, brought on at half time at Soccer City on Friday, is expected to take the place of Lucas Thwala, but Parreira said he would not confirm the line-up until he had told his players overnight.
"But now is not the time to change the team. What we will do is make some tactical adjustments.
"We will have a different approach from the Mexican match, because they are the most daring team of the competition and we had to deal with them differently to Uruguay."
He said he expected his side's next opponents to play with three centre-backs, as they did last Friday in their goalless draw with France in Cape Town, and look to use the counter attack.
"Diego Forlan is a player we can't leave free," Parreira said of Uruguay's leading striker. "We have a plan for him. Every time when we played against him when I was coach of Brazil, he scored."
South Africa captain Aaron Mokoena told the same news conference he hoped for more vociferous home support in Pretoria on Wednesday.
"We want to hear those vuvuzelas," he said in a reference to the controversial plastic trumpet blown throughout the World Cup games in South Africa.
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