"But if it floats towards the ceiling, which is impossible, that's me losing and not running fast.
"I just replay that over and over in my head, that the reality of the ball floating up doesn't exist."
At that point, you really want to speculate, what if the ball is actually a small balloon filled with helium, but you remain silent for fear of disrupting the space/time continuum - or at least Millar's version of it.
Sprinters are different to other athletes. They tend to be physically and emotionally more highly strung than their counterparts in other events, and Millar surely demonstrates those traits, both before and after the starting gun sounds.
His home-straight blitz had eclipsed Chris Donaldson's 18-year-old national resident record by almost one-tenth of a second, a significant margin over such a short distance.
"I knew from the first step that I was moving," Millar reflects. "I knew I was in front of everyone else, and then just tried to put it down and focus on good mechanics - feeling light, but also feeling good and powerful.
"I just knew, once I crossed the line, that it was over a lot quicker than other races."
In fact, Millar's mechanics are the area he has probably made the biggest gains in recent times. When coach Dr Paul Gamble first met his protege in June 2015, he found Millar "a broken man".
His technique was contributing to a series of niggling injuries that were clearly inhibiting his development, so their mission was to deconstruct that flawed style and rebuild it.
"We returned to fundamentals and a lot of ABC-type drills to piece together the different parts of his technique," Gamble told athletics writer Steve Landells.
"We focused on quality, rather than volume. We worked on many aspects, like how his feet connected to the ground and the finer, deeper nuances of sprinting."
Millar, 24, echoes that observation.
"Last year was a big year for me to relearn how to run and get a really good understanding of my body.
"There were a lot of things we did right, a lot of things we could have done better, but acknowledging that we didn't have a perfect run and then figuring out how to do this year properly."
Almost 48 hours after eclipsing the dash record, Millar went one better, clocking 20.37s over 200m to smash the resident record and dip under Donaldson's national mark, set 20 years ago in Melbourne.
Again, he showed his flair for the mangled metaphor, claiming to have literally run out of his skin in the 100m. In an earlier interview, he had reportedly described how he could feel himself running ahead of his body.
But Millar is also prone to the odd brush with officialdom and went close to ejection from the shorter race for time-wasting. Struggling to anchor his blocks at the startline, he was denied permission to have someone stand on them and eventually secured them with a pile of spare blocks, far from ideal preparation.
"I had to find a way to flip that to my advantage, so getting pissed off was the best thing I could do," he says. "Some people wouldn't have liked it, but I just thought 'bring it on ... annoy me, irritate me and see what happens'."
By now, it's clear that Millar's dramatic improvement is as much mental as physical and he admits the day he stood next to sprint superstar and eight-time Olympic champion Usain Bolt proved an eye-opener.
The pair went head to head over the rarely raced 150m at the Athletics Australia Nitro series in February, with Bolt predictably easing away, but Millar clearly better than the rest.
"I felt like a spectator there," he said. "But every time I run against guys like that, it seems to elevate me to a different level.
"You can watch them on YouTube, but until you see them in the flesh, they don't become real, malleable things.
"It's the realism of running sub-10 ... if you can see and touch it, you can believe it."
Kiwi speedsters are a rare breed. Isolated from the rest of the world, we've tended to forge our track and field reputation on middle and long distance running, and more recently, throwing.
New Zealand's fastest 100m exponent is still Ghanaian-born Augustine Nketia (10.11s), who settled here after representing his country at the 1990 Auckland Commonwealth Games. That only reinforces the challenges involved in producing home-grown sprint talent.
"Growing up and coming through the ranks, being told that New Zealand wasn't a sprinting nation, I'd always thought that there always has to be a first," says Millar.
"I really hope that, if I don't go any further than this, I've done enough to help some of the guys coming through to see that this sort of thing is possible, no matter what people say.
"Just don't take no for an answer."
Even though his 200m performance will earn an automatic invitation to this year's IAAF world championships, Millar may yet be on a collision course with Athletics NZ selectors.
After his 100m, Millar is confident that run will get him to the start-line in London over the shorter event, even though it's still six-hundredths of a second outside the international qualifying standard.
Following the 200m, he is even surer that he can piggy-back off this performance into the 100m field.
"Stunning, absolutely fantastic," enthuses ANZ convener of selectors Graham Seatter, moments after the historic half-lap. "Joseph's made a major breakthrough."
Millar can start packing his bags, certain to be named in the first batch of selections on April 13.
But Seatter insists Millar will still need to crack 10.12s to seal his 100m spot at London.
