The experienced scrumhalf has battled his way back from two serious injuries over the past 18 months and up until a few weeks before the tournament was unsure he would play in England at all.
But now he wears the captain's armband for the Springboks in their knockout fixture against Wales at Twickenham on Saturday, his body so far holding up to the challenge and his performances spurring on a side that were in shock following their 34-32 loss to Japan in their opening fixture.
"Originally I was only going to start (the fourth pool game) against USA, but after the Japan result we had to make a decision and I was happy to follow that," Du Preez told reporters on Friday.
"I worked hard last June to get back onto the pitch after a career-threatening injury and was injured again later on playing in Japan. Up until two weeks before the start of the World Cup I wasn't sure if I could play rugby.
"It's been a physical and mental battle to get to this point, and I certainly never thought I would captain the team. It's been quite a journey for me."
Since being selected to start the second pool game against Samoa ahead of Ruan Pienaar, the 2007 World Cup winner's accuracy and decision-making have been crucial in getting the team's campaign back on track.
Typically modest, he said credit should go to the entire squad for the way they picked themselves up from the depths of despair to beat Samoa, Scotland and the U.S.
"The Japan game was a massive shock, but after that match it could have got much worse. If we lost the next two games we would have gone home as the worst Springbok team in history.
"I'm very proud of the way the guys stood up after that."
South Africa coach Heyneke Meyer described Du Preez as a genius this week and Wales have been equally generous in their praise.
"He is a guy I have admired for many years and has slotted straight back into their team," Wales defence coach Shaun Edwards said.
"It's no coincidence the Springbok machine is going at full throttle since he came back in. He is a magician on the rugby pitch." (Editing by Justin Palmer)
