“That thought was going through my mind every day,” he admits. “It was the first time in my life I didn’t know where I was going.”

It was early 2017 and O’Leary felt marooned, 20 years old and far from home in his second year of a scholarship at Iona College in New York.

Up until then, his sporting career had galloped along with the pleasing pace of a promising thoroughbred, but suddenly he was broken goods.

O’Leary comes from a family well versed in success, both sporting and otherwise. His father Eddie is racing manager of Gigginstown House Stud, a powerhouse in national hunt racing; his uncle Michael is the CEO of Ryanair, while his cousin Rowan Osborne is an underage rugby international.

Tomorrow morning O’Leary’s mother and two sisters will be in Tilburg, the Netherlands, for his return to the European Cross Country Championships, where he will don the Irish vest in the U23 race. His father, however, will have to watch from afar in France, where Eddie is attending a horse sale to find the latest recruits for Gigginstown.

Indeed when he talks about tomorrow’s race, Jack reaches for lingo he’s learned from a lifetime in racing. “It’s a very, very similar game and that’s why my Dad has a big interest – when he talks about running he can always give me advice. My plan is to get out the front, compete, and with Gigginstown horses that’s always the goal: if you’re not in that top pack you’re not going to win.”

But success for O’Leary will not be defined by his place at the finish line, more his presence on the start line. He thought he might never be back.

In 2016 he finished a superb sixth in the U20 race in Chia, Italy, but midway through he picked up a hip injury that would plague him for months. “My hip bone got wedged into the socket on one of the mounds,” he says. “A month later I was training and getting ready for the track season and I got an injury in the tibial tendon in my ankle.” The problems were related: the ankle issue was caused as O’Leary compensated for his hip problem.

He barely ran for five months, until his career, like so many others, was eventually rescued by Gerard Hartmann, the renowned physical therapist who had him back in action after two weeks of treatment. But after returning to Iona last year, O’Leary sustained a back injury that wrecked his autumn campaign, forcing him to toe the line at the NCAA Cross Country last November with his only mileage logged on an anti-gravity treadmill.

Some question the merits of the US scholarship system, but O’Leary only has good things to say. “I was thinking, ‘have I made the right decision, why is everything going wrong?’ but I know absolutely I’m in the right place,” he says. “The people worked with me and were always positive, there was no sense of urgency. They said, ‘fix your body, you’re here for five years, not five months.’

“Ireland is amazing and does the best they can, but the depth of America – it’s a world level and it makes you into a better athlete.”

This year O’Leary returned to the NCAA Cross Country in much better form. He was inside the top 100 in the 250-strong field for much of the race but faded close to home to finish 139th.

Tomorrow he will join forces with an Irish U23 team that looks capable of winning a medalIt includes Ryan Forsyth, who finished 11th in the NCAA Cross Country, and Brian Fay, a promising 20-year-old who ran a four-minute mile earlier this year and finished fourth in the senior race at the National Cross Country last month.

“There’s a medal there if everything goes to plan and we all race our hearts out,” he says. “I think I have a huge race in me but to have an Irish singlet on me again is the biggest achievement after all that’s happened.”

The best Irish medal chance of the day will be in the junior women’s race, where rising star Sarah Healy will pit her considerable talent against Europe’s best teenagers. The race will be streamed live on the European Athletics website at 9:45am Irish time, with delayed coverage on RTÉ Two from noon. Healy was an impressive winner of the Irish U20 title last month and though little separates her and chief rival Delia Sclabas of Switzerland, the soft underfoot conditions after days of steady rain are sure to play into the hands of the 17-year-old Dubliner.

“I’m going to go out there and race it, give myself a good chance and see what happens,” said Healy, who won two gold medals at the European U18 Championships this year. “This is less daunting because there’s less pressure. The competition is better but it’s less scary.”

The Irish senior teams will be led by national champions Ciara Mageean and Kevin Dooney, though it will come as a huge surprise if either can contend for a medal. Stephen Scullion was a late withdrawal from the senior men’s team after picking up a viral infection while travelling, with Damien Landers of Ennis drafted in as a worthy replacement.

European Cross Country Championships, Live: RTÉ Two, 12pm.