Phelan was born in Ireland. Immensely strong for his size, the Townsville forward was playing for Brisbane's Southern Suburbs club when he first was first selected for Queensland at lock in all three games of the 1981 interstate series. Phelan was the Brisbane Rugby League premierships Rothmans Medal winner that year and also won the Grand Final with Souths.
Phelan signed to Sydney's defending premiers Parramatta in 1982. He had to sit out the start of the 1982 while Parramatta waged a battle with the Queensland Rugby League over his transfer fee.
He played at prop in the Eels' two Grand Final wins over Manly in 1982 and 1983 but moved to the second-row for the 6-4 loss in the 1984 decider against Canterbury. In 1984 he was recalled to the Queensland side for game III of the State of Origin series where he appeared at second-row.
After a season with Oldham in England, Phelan returned to his home state in 1985 and continued playing with Souths, helping them to victory in the 1985 Brisbane Rugby League grand final.