[1] His paternal grandparents were from Donegal in Ireland,[2] and he grew supporting Celtic.
[3] After playing youth football for Rangers, and spending loan spells at Edinburgh City, Dumbarton and Clyde,[4][5][6] as well as in the United States with Orange County SC,[7] Shiels signed for Hamilton Academical in summer 2021.
[8][9][10][11][12][13][14] Shiels left Hamilton in June 2023[15] and re-joined Dumbarton in August 2023[16] scoring his first goal for the club in a 4–0 victory against Bonnyrigg Rose in November 2023,[17] in a game where he also won a penalty and provided an assist.
[19][20] He left Cove after just eight appearances,[21] and returned to Dumbarton on a season long deal in the summer of 2024.
[28] On signing for Dumbarton in August 2023 he said he preferred playing in a more attacking role.