Thinking back, the signs have been there for a while, the unmistakeable traits of an athlete equipped to go as far as she dares to dream.
An endurance engine that can set out at a punishing pace, then sustain it; a late-race change of gear that can crush the spirit of rivals in an instant; a curiosity to quiz her coach on the science of training, coupled with an astute knack for the artistry of racing.
Sarah Healy may be a two-time European U-18 champion, the fastest 17-year-old middle-distance runner in the world, and igniting all kinds of hope among the success-starved ultras of Irish athletics, but she remains refreshingly well-rounded for such a precocious prodigy.
This, at her age, is perhaps most important of all if she's to go the distance in this sport.
Back in March 2017, at the Irish Schools Cross Country in Belfast, this writer was told by colleague Feidhlim Kelly to look out for an athlete in the intermediate girls' race - adding that it would be easy to tell which one he was talking about.
And it was.
Despite losing one of her spiked shoes early in the race - the kind of glitch that usually sinks an athlete's chance in heavy underfoot conditions - Healy brushed it off and motored away from her peers, one foot slipping, one foot gripping the entire way around.
It was the kind of grit her coach Eoghan Marnell first witnessed four years earlier at an U-13 600m race in Tullamore. Healy got bumped badly with 200m to run and dropped out of contention for the win, but something in the way she reacted spoke volumes.
"Even at that age, she stayed calm and started chasing down the lead group," he says. "She was incredibly determined coming up the home straight, clawing back the leaders, and managed to get up for bronze."
Her star has been ascending ever since, even though athletics proved an acquired taste for Healy, who was first brought to Blackrock AC by her mother at the age of nine.
"I didn't like it that much then," she says. "But I love it now."
She first hit the headlines last summer when striking gold at the European Youth Olympic Festival in Gyor, Hungary, where she returned over the weekend to do the 1500m and 3000m double at the European U-18 Championships.
Watching trackside was Sonia O'Sullivan, whose daughter Sophie won silver in the 800m, and Ireland's greatest athlete has taken a keen interest in Healy's career, staying in touch with her through email in recent months.
"I think she's fantastic," says O'Sullivan. "She's been running amazing and regardless of being 17 years old or not, she's just a good athlete."
There is, of course, an obvious caveat when spotlighting the achievements of one so young, and it is this: most of them never make it. Whether it's their health, their motivation, or life itself that gets in the way, having underage success is a bit like that priest in Father Ted buying 2,000 tickets for the raffle: it increases your chances, but guarantees nothing.
Having come through the adolescent minefield to shine as a senior, O'Sullivan knows how tricky the path that lies ahead is.
"It's the really difficult stage she's entering into and it's very unpredictable. With girls, their bodies can change, there's lots of different factors like social things and if you're at such a high level, the only way to get better is often to run more, but how do you manage that: to run more without running too much?
"You just have to be cautious without being too cautious. Sarah probably overachieved this year, but she's not changing her plans so that's a good sign. She's got a good coach and is being well advised, so it looks like she's got everything under control."
Healy typically runs between 30 and 50 miles a week, about half the amount of a world-class senior, and for much of the year she still plays hockey with both her school Holy Child Killiney and club Avoca.
In the winter Marnell works her running around hockey training, and he believes combining the two at this age is the perfect recipe for long-term success.
"Sometimes that means the running sessions get bumped, but that is preferable to Sarah attempting sessions tired," he says.
"It's common knowledge that early specialisation is bad for an athlete, and yet the common practice is still early specialisation - that's just baffling. Sarah is a very accomplished hockey player and at only 17 there's no reason to give up something she loves."
Marnell notes the importance of Healy's family in supporting her ambitions, and when it comes to next year he's quick to highlight her main target: "The Leaving Cert."
With a personal best of 4:09.25, Healy could run at next month's European Senior Championships if she wanted, but that's never been the plan, so when they are on she'll be at Irish College in Killarney, her final race of the summer coming at next week's Morton Games in Santry.
The best American colleges are lining up with scholarship offers, but Healy is unlikely to follow that well-worn path next year.
"I think I'm going to stay here, that's the plan right now," she says. "I might study law or something like that - nothing really sporty anyway."
Long-term, the Tokyo Olympics should be within her scope, not that she's looking too far ahead.
"I'd love to go, but I haven't thought too much about it. Eoghan is always saying he's thinking long-term. There's still way more to add so hopefully I can get better."
She started gym work for the first time this year, though that's been put on ice for her racing season.
"It's very easy stuff, I'm pretty weak," she says with a laugh.
Right now, her options seem endless, but if there's one principle that's worked for Healy to date it's Leonardo da Vinci's line about simplicity being the ultimate sophistication. With a talent so great, there's a temptation to reach for unhelpful comparisons with past prodigies, but that does a disservice to an athlete setting out on a journey that could end just about anywhere.
"It's the nature of the sports fan to crave the next Sonia or Fionnuala, those athletes have brought a lot of joy to Irish people," says Marnell.
"But Sarah won't be the next anyone, she'll be the first Sarah Healy and you'll get 100pc from her, however far that takes her."