The two teams will lock horns at the Mercedes-Benz Stadium in Atlanta on Thursday evening in what is effectively a must-win match for both nations after disappointing starts to their campaigns.
Czechia suffered a defeat to South Korea in their opening Group A fixture, while Hugo Broos' men were beaten by tournament hosts Mexico.
With both teams still searching for their first points of the tournament, Koubek believes his side can respond positively and revive their World Cup hopes.
"I'm not nervous. I would call it a healthy tension. I'm not nervous before a match that I'm going to collapse, no. I always feel tension, but I think it's good, that it's right," Koubek told the Czech national team's official website as quoted by Kickoff.com.
"Of course we know that we are in the same situation as our opponent. That we came out of the first round empty-handed. So of course, it is a complication, but there are still six points at stake and now the first three are on offer. Of course we have the utmost desire to get them."
The Czech coach has admitted he was intrigued by South Africa's tactical setup against Mexico and expects Broos to make adjustments for Thursday's encounter.
"South Africa chose a slightly unconventional style against Mexico. I think they gave preference to players of a different typology than those who play standardly. The formation was changed a bit, so I don't expect exactly the same performance now," said the coach.
Koubek also highlighted the areas where he believes Czechia must improve if they are to get the better of Bafana.
"We have to eliminate the opponent's strengths, mainly in terms of breaking. We definitely want to be more dangerous up front, the Koreans didn't allow us to do that much. But this is a different opponent."