"I just thought let me just do it. I didn't see anybody else doing that job," de Kock said.
Although South Africa could have used either Stiaan van Zyl or Temba Bavuma, de Kock thought the 16 times he has opened in first-class cricket would stand him in good stead to do it in Centurion, and take the heat of a team-mate who had tried and failed to do it before. "I have a bit of experience at opening in red-ball cricket. I thought that since Stiaan has had a go, let me just rather go there and do it and do what I can for the team," de Kock said.
Despite scoring 82 runs and featuring in the first century opening stand since 2013, when asked if it is something he would consider doing again, de Kock said one word: "No."
He admitted he found it difficult to stay defensive for as long as he did, although he was pleasantly surprised by his own restraint, which had him see off 79 dot balls. "Opening in Test cricket is an under-rated job. It's a different level, it's not the same as opening the batting in one-day and T20 cricket. The ball moves around a lot and it tests your technique and your patience," de Kock said. "I actually learnt a lot about myself, like where to be tight and how to play certain balls. I think it's the most I've ever left a ball in my career. I am proud of myself for doing that. It's quite nice knowing that I can do that."
And now that he knows, he is happy to hand the reins back to Elgar when he recovers from four weeks on the sidelines. "I think that's more for Dean and Stephen. I'll stay at six and seven, thanks," de Kock said.
In this match, though, de Kock will have to open the batting again. He is fairly confident the surface will not get any more challenging than it was on the first morning. "I think it's going to stay the same and maybe get a bit quicker. This morning it was soft and spongy, but it's a good wicket. I think we can take the match five days."
If that happens, it will likely mean de Kock will also spend a significant amount of time in the field but he is not too concerned about the effect that may have on his batting later on. "We'll have to see the situation, but I am just going to keep my mind open."
At least conditioning is not an issue for him. De Kock has spent some time training with former international Mark Boucher and the biggest takeaway was a focus on fitness. "He just grinds me, makes me work hard. He loves the fitness part of keeping and I feel fitter," de Kock said. "It's the stuff I know but he just does it to an extreme level."
For now, de Kock can put his feet up a little and watch the rest of the line-up build the South African total. He is particularly hopeful of JP Duminy reaching three figures after a lean patch that has stretched back more than two years. "JP has been working very hard lately. For him to score a hundred will be a massive boost. I hope he does," de Kock said. "It will be nice to see a team-mate who has been under pressure off the field do well."