As chief executive and project manager of South Africa's burgeoning Institute of Sports Science, the manager of Francois Pienaar's 1995 World Cup- winning side now lords it over one of the most ambitious sporting research and development enterprises in the world. "These are early days, but we have achieved initial results I find extremely exciting," he says, his voice alive with the passion and energy he once brought to bear on, among others, the All Blacks of 1976 and the Lions of 1980.
"We called in a hand-picked, elite Under-19 rugby squad, tested and evaluated them and sent them off with a programme to follow. Three months later, their muscle mass had increased by two kilos - two kilos, I say - yet their weight was exactly the same. Incredibly encouraging, don't you think?"
Then the craggy smile makes way for an expression of the utmost seriousness. "But of course, we cannot afford to deal only with the elite. Elitism is a sensitive issue in a society such as ours because so many of our under-privileged people still have no support system that allows them to flourish in the sporting sense. Most South Africans recognise that our rugby and cricket teams in particular need to reflect the diverse nature of the population and the process needs speeding up, but to bring non-whites through on merit is a major challenge, one which demands that we take our expertise out into the country areas where it will really make a difference."
Du Plessis' extraordinary sporting odyssey - from captain of the Boks in the dark days of isolation to progressive icon in the age of the Rainbow Nation - is far from finished. Clearly the task he has undertaken at the business-funded, university-linked, non-profit making institute will, he imagines, keep him occupied for the foreseeable future and beyond. Yet rugby, pure rugby, is never far from his thoughts, especially now that the Lions are in town.
"There is such excitement in South Africa about the Lions because they carry a mystique that no other side possesses - a mystique that has increased since they were last here 17 years ago. We've seen so much of the New Zealanders and Australians that we are becoming almost blase about them. But the Lions? There is no problem generating interest in a Lions team.
"I first played against them in 1974 and even though my children were not around then, they know everything there is to know about Willie John McBride's great side. I would unhesitatingly say that along with last year's All Black team, the '74 Lions were the greatest to visit this country since the war. One-eyed South Africans might say they caught Springbok rugby at a weak moment, but no. The Lions were the ones who weakened us through their strength."
In Du Plessis' view, Springbok rugby is in rude health despite last year's first-ever home defeat by New Zealand and the subsequent downfall of Andre Markgraaf, whose coaching career crumbled abruptly under the ignominy of a racism scandal after disaffected provincial players secretly recorded him using language of almost unbelievable crassness. "The Markgraaf business was so unreal I don't think it ever became the stumbling block to progress that some of us feared. It was too bizarre to be of lasting damage.
"We have our ups and downs here, but the Lions will find us very competitive. It is too early to say how the tourists will shape up for the Tests, although they have to start putting things together fairly quickly now the early games are behind them."
Given that Du Plessis' love of rugby remains undiminished, does he not pine for the visceral excitement of direct contact with the sport he once mastered so supremely as a fast, ruthless and prodigiously skilled No 8? After all, it was his managership, allied to the coaching of Kitch Christie and the enlightened public relations contribution of Ed Griffiths, that made the Springboks world-beaters off the pitch as well as on it during the glory run to the Webb Ellis Trophy two years ago.
"I'm thankful for the privilege of managing the Boks and I certainly miss match day on the bench, but I never had any long-term designs on rugby officialdom," he insists.
"I carried on for a while after the World Cup but Kitch became ill and I had a decision to make: would it be this, or my career. As I was very involved in the institute project, I said: 'That's enough.' I'm not saying I'll never be involved again, but in the medium term, the institute is my only priority."Reuse content