Caster Semenya and Willem Coertzen will start their Olympic campaigns on Wednesday, while Lehann Fourie and Anaso Jobodwana will strive to make the finals of their respective events.
Semenya goes into the morning heats confident that her controversial victory in the 2009 world championships is a thing of the past.
The 21-year-old – who is coached by 2000 Sydney Olympics 800m champion Maria Mutola from Mozambique – had to undergo drug tests followed by gender tests following that magnificent victory in Berlin.
The situation spiralled out of control with Semenya complaining of "unwarranted and invasive scrutiny of the most intimate and private details of my being".
She was barred from the track for almost a year before being cleared to run again and her comeback was hampered by a lower back injury and a growing belief that coach Michael Seme had taken her as far as he could.
"I don't have to entertain those things now. I can concentrate on my running, that's all."
However, she said on the eve of the Games: "That is in the past.
"You need to concentrate on the future. I don't have to entertain those things now. I can concentrate on my running, that's all.
"With each year I experience I become a more relaxed athlete. I also know what is important to listen to and what to ignore. I try to run my best always but sometimes I do not and I have to deal with negatives. People ask questions that can make you sad, but I must always stay positive.
"That's what I have to learn. I have to act professionally. But this is my first Olympics so it'll be special for me."
Semenya will most likely not have a lot of difficulty proceeding to the semifinal in her event. Rose Almanza (CUB) and Alysia Montano (USA) are the only other athletes in heat 1 who have recorded times under 2 minutes this season.
Almanza was timed at 1:59.55, while Montano’s best is 1:57.37. Semenya has run two races under two minutes this season, one in Pretoria on 20 April and again on 6 July in Germany. Her times were 1:59.58 and 1:59.18 respectively. Semenya will be in action at 12:35.
Semenya recently changed coaches and appointed Maria Mutola, a former Olympic 800m champion from Mozambique, in order to achieve the best at the Olympic Games.
Willem Coertzen will make his Olympic debut in the gruelling decathlon, a competition that stretches over two days, consisting of ten disciplines.
He will face a tough field which includes world record-holder Ashton Eaton, who set the record at the US Olympic trials in Oregon only last month.
Day one will comprise the 100m, long jump, shot put, high jump and 400m, followed by the 110m hurdles, discus throw, pole vault, javelin throw and 1 500m on the second day of the contest.
Coertzen currently holds the South African record of 8244 points, after winning the National Championships in Port Elizabeth on 14 April.
Anaso Jobodwana and Lehann Fourie will compete in their respective semifinals in Wednesday's evening session.
Jobodwana will be in action at 9:10pm CAT (SA, GMT+2) in the 200m and Fourie’s 110m hurdles semifinal will take place at 8:15pm, followed by the final at 10:15pm.
Additional reporting: Sapa-AFP