Mac Niallais arrived in 2014 having played around a half-an-hour of meaningful senior inter-county football for Donegal. That year would bring his first league start -agaiainst Laois at O'Moore Park. He palmed home a goal in the twelfth minute and scored a point later in the same match. The year also brought games in the Senior Championship for Mac Niallais for the first time. Called onto the field when Donegal were forced to make emergency reparations to the midfield following injuries to Rory Kavanagh and Neil Gallagher, Mac Niallais collected the man of the match award in the Ulster semi-final against Antrim at Clones. He then won his first Ulster senior title, helping himself to three points in the final against Monaghan.
^ abDuggan, Keith (24 June 2014). "Odhrán MacNiallais now at the heart of Donegal's championship drive: Gweedore man repaying the faith Jim McGuinness has shown in him". The Irish Times (Irish Times Trust). Retrieved 24 June 2014. Yesterday, he was at the heart of Donegal's drive to a fourth consecutive Ulster final and finished his day in front of the television cameras accepting his first man-of-the-match award in the competition. [...] Both of MacNiallais's championship starts have had a touch of improvisation about them. Just as they did against Derry, the Donegal management was forced to make emergency reparations to its midfield after Rory Kavanagh was unable to recover full fitness and Neil Gallagher broke down after 17 minutes. [...] The Gweedore man was just 18 when McGuinness first called him into the squad and ran the eye over him in McKenna Cup games against Tyrone and Fermanagh in the winter of 2011. Injuries upset his progression that season, curtailing his club career also and it wasn’t until last year that he resumed county training.