The two nations currently leading the way in Group A of qualifying for the Africa Cup of Nations will meet on the artificial surface of Pointe-Noire's Stade Municipal.
Congo boast maximum points after two games and sit two points clear of South Africa, but Mashaba expects his inexperienced team to rise to the occasion this weekend.
"When it comes to football, we have no fear, we are confident in ourselves and our abilities," said South Africa's coach.
"What maybe keeps me awake at night is the hostility we will face off the pitch, from the fans and so on. They could make it very unpleasant for us.
"It is not something we will harp on to the players about though. The squad we have selected is robust and they have already shown great mental strength."
Mashaba insists there is no chance of South Africa playing for a draw in Pointe-Noire, ahead of Wednesday's return match in Polokwane.
"We will not settle for anything; we want maximum points," he added.
"If we got six points from these two games - and I would love to see these boys do that - then we make life easy for ourselves.
"We could play the final two games [against Sudan at home and Nigeria away] with no pressure, knowing we can afford to draw one, maybe even lose the other.
"That is the position we want to put ourselves in."
It will be the ninth meeting between the two sides since South Africa were readmitted to international football in 1992, with Bafana Bafana having won four, lost one and drawn three of the previous meetings.
However, the visitors are set to face a stern test on this occasion, with Claude Le Roy's Congo having claimed a home victory against Sudan and an impressive 3-2 triumph away to continental powerhouses Nigeria.
In the build-up to the game against South Africa, Le Roy acknowledged that his side's victory in Nigeria was something very special.
“Even in my more stupid dreams I never thought that we could have beaten them," he said.
"Possibly they did not prepare psychologically for the game against us as they would have if they had played France or Brazil, but we were ready for them, even if we were missing some players.
“Although we had some young players they were not overwhelmed. They went into the game knowing that they had nothing to lose and even though we do not have players like the Super Eagles who play in clubs like Chelsea, Monaco and Lazio, I think some of our players could play at the highest level."
Congo are now up to 48th in the FIFA world rankings, the highest position they have ever occupied.
“The people [of Congo] are more than surprised," Le Roy added.
"To be ranked 48th is unbelievable, but our confidence is also very great and we are now looking forward to our next games."
