McFadden's father and older brother played football and encouraged his own interest. McFadden is left-footed (i.e. ciotóg). He played at older age grades from early on. He was a county player by under-16. Himself and Christy Toye, who was in his class at primary school and would later play alongside him many times for Donegal, played in (and won) the Ted Webb under-16 tournament, the same year they were part of the minor team. McFadden also played under-21 for his county while still playing as a minor. While at Galway, the then Donegal manager Mickey Moran noticed him. As well as being at university, McFadden was at this time in his third year at minor, leading Moran to assume McFadden was older. McFadden sat on the bench for a Donegal game in Tuam and did not play. After this, Moran approached McFadden and advised him to concentrate on playing with the minor team, telling him that he would be interested in reviewing McFadden's progress the following year.