McDonnell first became involved as a selector at inter-county level with the Cork senior hurlers in 1986. A 2–18 to 3–12 defeat of Clare secured a record-equaling fifth successive Munster title that year. This victory paved the way for an All-Ireland final meeting with Galway. Galway were favourites against a Cork team seen as being in decline, however, on the day 4 Cork goals, one from John Fenton, two from Tomás Mulcahy and one from Kevin Hennessy, helped Cork to a 4–13 to 2–15 victory.