It's a decision every talented young athlete eventually has to make - and it's not an easy one. Being gifted at multiple sports can be both a blessing and a burden, your ability tugged in different directions as the ominous threat of burnout begins to loom overhead.
Darragh McElhinney, a dual star of a very different kind, was forced to abandon his first love last summer, but football's loss has been athletics' gain, and right now he's got a good thing going.
The 17-year-old is the brightest young star at tomorrow's All-Ireland Schools Cross-Country in Mallusk, where barring any mishaps he should cruise to the intermediate boys' title.
A year ago, however, McElhinney was like a street performer with a dangerous number of plates spinning overhead, balancing international athletics with inter-county underage football for Cork.
He comes from Glengarriff, a village nestled on the Cork-Kerry border where Gaelic football was, is and forever will be king. Thing is, McElhinney had conquered Ireland's best at middle-distance running and was starting to make his mark internationally.
In June, he got a text from the Cork trainer with the summer schedule, but when he plotted it alongside his racing plans, McElhinney knew something had to give.
"I didn't have time for football training and my club realised that so I just played the games," he says. "It was harder to do that with Cork. I told him there and then; there was no point doing this half-arsed."
That's where his inter-county career ended, though McElhinney helped his divisional team Beara to the county title in October.
"That was a nice way to go out," he says. "It was tough to tell them, but they realised to keep running at a high level you have to give it the commitment."
He got an insider's look at what would eventually be required a month later, with his coach Steven Macklin inviting him to join the Irish pre-Olympic training camp in Uberlandia, Brazil.
He assisted with pace-making for modern pentathletes Arthur Lanigan O'Keeffe and Natalya Coyle, who Macklin was coaching, then hung out with the Irish team, soaking up every word of advice they offered. Between sessions they even squeezed in a trip to Rio to watch some boxing and beach volleyball.
When he returned, it had the effect Macklin desired, lighting a fresh fire under McElhinney. His training increased from four to six days a week and he emerged better than ever, breaking John Treacy's Irish indoor youth record for 3,000m last month - his time of 8:18.88 the fastest in the world by an U-18 this year.
The European Junior Championships will be the focus of his summer, but given his Rio experience, I can't help but ask if he sees himself as part of the next Olympic team in Tokyo.
"2020 might be a bit soon," he admits, before reeling off a list of times and championships he sees as essential steps towards the top. "Then, if I can keep progressing, the Olympics in 2024."