University During his studies at
St Patrick's College in
Maynooth, Stack was an automatic inclusion on the college hurling team. In 1973 he was at left wing-back as St Patrick's faced
University College Galway in the inter-varsities final. A narrow 2–12 to 4–4 victory gave Stack a first
Fitzgibbon Cup medal. St Patrick's reached the decider for a second successive year in 1974. A 2–10 to 1–7 defeat of
University College Dublin secured a second successive Fitzgibbon Cup medal for Stack. Stack was also a regular member of the starting fifteen over the next three years; however, St Patrick's faced defeat in three successive championship deciders.
Club Stack was still a minor when he was drafted onto the Sixmilebridge senior team in 1971. He was at left wing-forward as Sixmilebridge faced
Tubber in the intermediate decider. Stack top scored with 1–2 as Sixmilebridge secured promotion to the senior ranks following a 4–14 to 4–4 victory. After defeat in the senior decider in 1976, Sixmilebridge returned to contest a second successive county final the following year against
Kilkishen.
Mickey White was the hero for Sixmilebridge as he lofted the winning point seventy five seconds from the final whistle to secure a narrow 1–6 to 1–5 victory. Not only was it a first
championship medal for Stack, who had the honour of captaining the team, but it was a first title for Sixmilebridge. Two-in-a-row proved beyond Sixmilebridge, however, the team contested the decider again in 1979. Despite playing against the breeze in the first half Sixmilebridge led by 2–4 to 0–5. The Bridge powered on in the second half to claim a 5–11 to 0–9 victory over
St. Brendan's. It was Stack's second championship medal.
Éire Óg defeated Sixmilebridge in the 1982 decider, however, both sides were back in the final again the following year. After a 1–10 to 3–4 draw, Sixmilebridge triumphed in the replay following a 1–10 to 1–7 victory. It was Stack's third championship medal. The centenary year of the
Gaelic Athletic Association saw Sixmilebridge make history by retaining the title. A narrow 3–7 to 1–12 defeat of
Clarecastle courtesy of a late
Gerry McInerney goal gave Stack, who was captain and manager of the team, a fourth championship medal. He later secured a
Munster medal following a 4–10 to 2–6 defeat of
Patrickswell. After a five-year lapse Sixmilebridge claimed the championship again in 1989. A 3–14 to 1–11 defeat of Clarecastle gave Stack a fifth championship medal. Stack secured a sixth championship medal in 1992 as Sixmilebridge defeated Éire Óg by 1–11 to 1–10. For only the second time in the history of the club, Sixmilebridge retained the championship in 1993. A 3–8 to 2–6 defeat of
O'Callaghan's Mills gave Stack a seventh championship medal. He retired from club hurling following a defeat by
Toomevara in the subsequent provincial campaign.
Inter-county Stack first arrived on the inter-county scene as a member of the Clare minor team. In 1971 he was
captain of the side that faced a 6–13 to 3–5 walloping from
Cork in the Munster decider. After progressing onto the under-21 team he faced narrow
Munster U21HC defeats at the hands of
Tipperary in 1972 and
Waterford in 1974. Stack made his senior championship debut on 7 July 1974 in a narrow 1–8 to 1–7
Munster SHC semi-final defeat of
Tipperary. After a fifteen-point defeat by
Kilkenny in the league final in 1976, both sides faced each other again at the same stage the following year. A 2–8 to 0–9 victory gave Clare the title and Stack a
National Hurling League medal. Clare later faced
Cork in the provincial decider, on a day when armed robbers made away with the takings from the gate of £24,579 during the second half of the game. Clare conceded an early penalty, but fought back to take the lead until a contentious red card for full back
Jim Power turned the tide for Cork and they fought on win by 4–15 to 4–10. Clare retained their league title in 1978, with Stack as captain collecting a second winners' medal following a 3–10 to 1–10 defeat of Kilkenny once again. In a repeat of the previous year, Clare faced Cork in the subsequent Munster SHC decider. In one of the worst ever provincial deciders and only the second one ever not to produce a goal, Clare were narrowly defeated by 0–13 to 0–11. This defeat demoralised Clare; however, Stack lined out in another Munster SHC decider in 1981. A 3–12 to 2–9 defeat by
Limerick was the result on that occasion; however, Stack ended the year by collecting a
GAA All Star Award. In 1986, Stack played in a fifth and final provincial decider. Victory eluded him for the fifth time, as Cork secured a 2–18 to 3–12 victory. Stack retired from inter-county hurling following a league game against
Wexford in early 1987.
Inter-provincial Stack also lined out with
Munster in the inter-provincial hurling competition. He first played for his province in 1980, however,
Connacht were the victors on that occasion. Stack continued to play for his province for another few years and captured two
Railway Cup medals in 1984 and 1985. ==Honours==