Rohan Browning admits it could be lurking anywhere.
It could be in what he eats for dinner, or up to the vagaries of the weather.
It's so small and imperceptible that searching for it could drive him to neurosis.
But it's also the main motivation for the second-fastest man in Australian history.
"It" is those couple hundredths of a second that he needs to break the 10-second barrier, in the men's 100 metres.
"I'd be lying if I said it wasn't always in the back of my mind whenever I race," Browning told ABC Sport from his training base in Rome.
"That is, to some degree, an arbitrary marker, because the depth of the event is so strong now [that] sub-10, or 9.99, doesn't guarantee that you'll make an Olympic final.
From impostor to the real deal
Only one Australian man has ever run under 10 seconds: Patrick Johnson clocked 9.93 in 2003.
Browning is now the second-best ever in this country after winning his heat at last year's Tokyo Olympics in a scintillating 10.01 seconds.
It was one of the biggest moments of the 24-year-old's career, as the "flying mullet" became an instant national hero.
However, he faded in the semi-finals, his 10.09-second run wasn't enough to progress to the final.
"I was really shocked by the reaction, and it was lovely and I felt incredibly well-supported," he said.
Browning has a chance to rectify that in a few weeks, when he'll contest the Athletics World Championships in the US state of Oregon, and the Commonwealth Games in England's Birmingham, back to back.
It's a chance for Browning to show how far he's come, and whether he can be considered among the world's elite runners.
And to do that, just sneaking under that 10-second mark won't cut it: 20 men have already achieved that this year.
How do you find those hundredths of a second?
Browning has been working with his coach, Andrew Murphy, and Athletics Australia's National Lead of Biomechanics, Dr Emma Millet, to break down his technique and identify where he can muster up even more speed.
Dr Millet says Browning's top speed is world class, but there's room for improvement in his start out of the blocks and his acceleration over the first 30 metres.
And, in such a short race, even the smallest factor can make a massive difference.
"It can be all about the positions that you are in the blocks and how you load your blocks," Dr Millet said.
"And it's been how do we tap into that feeling for Rohan, so that he can execute it on the day?"
There has also been a focus on ensuring Browning doesn't over-stride once he's out of the blocks.
"I think he's more than capable of running sub-10," Dr Millet said.
"He's done so well to do 10.01 and it wasn't a perfectly executed race, either, and that's where there's still heaps of room to move.
"What I'm focused on is trying to be as efficient as possible," Browning said.
"So I try to apply a critical mind to everything and, when working with my coach, we try to really focus on where we're going to get the greatest output, rather than just glorifying hard running, hard work, being tough all the time. We try to work smarter."
Browning is conscious of not being "paralysed by data", but he knows making what may seem like unnoticeable changes to the average observer, could be the difference between him being a good runner, and a great one.
And that's come with some growing pains.
He knows he hasn't raced at his best this season, and injuries and illness haven't helped.
"This year, we've really overhauled my race model to focus on trying to extend that acceleration a little bit and then hit top end speed a bit later, so that in the last 20 to 30 meters of the race, I'm not decelerating as much," he said.
"It makes you very error-prone, so that's something I'm trying to master now. And I think that's probably why I haven't run quite as quick as I would have liked to in some of the races.
"But I'm confident that, by the major championships, it'll come together."
He'll face his biggest test yet at this week's Stockholm Diamond League, in a field that includes the Olympic champion, Italy's Lamont Marcell Jacobs.
"I think he's one of the most technically efficient runners in the world," Browning said.
"And that's a significant reason why he's been able to be so successful at major championships under pressure, because he's able to maintain such a relaxed disposition."
Dr Millet says Jacobs' run in the Olympic final was near perfect, and something for Browning to draw inspiration from.
"Marcell is one of those ones [who] you saw in Tokyo, where his ability to get out of the blocks, has a great top speed and not decelerate, he was able to execute a really good race," she said.
"He was a 10-second runner, and then has, last season [has] gone well below and managed to really execute it in the final."
Finding his 'perfect day'
While 2022 hasn't gone exactly to plan for Browning so far, he's optimistic he can pull everything together come the World Championships and Commonwealth Games.
"I want to be in the final and then I want to try [to] execute the best race that I know how and I'll see where that puts me in the world," he said.
And it's not just about collecting silverware, or running sub-10s.
"What I'm really focused on this year is bringing my average performance down and not having those outliers," he said.
"I want to be as consistent as possible, as unglamorous as that is, so that I know what I'm capable of when it comes to big moments in the major championships.
"Rather than celebrating the glittering moments of brilliance that are just very transient. It's all about doing it when it counts."
Browning is also a big believer in balance.
For him, that includes studying law at Sydney University, spending time with his friends and family, and playing golf, even if he is a self-confessed hacker.
"It's so important to decompress. That helps get the best out of yourself on the track."
Browning has also tapped into some of Australia's greatest athletes — such as Cathy Freeman and and Steve Waugh — for advice along the way.
And the prospect of having a moment like Freeman's 400m victory at the Sydney Olympics, or Waugh's "perfect day", last ball century at the SCG are tantalising.
"Every athlete romanticises the idea of having a moment like that in their career," Browning said.
"There's a Brisbane Olympics coming up in 2032. I think I'll be 34 by then, so I'll see if I'm still around.
"I think the prospect of a home Games and [2026 regional Victoria] Commonwealth Games definitely inspire me to keep pushing."
