Molloy played lock for the Ireland national rugby union team, earning 27 caps from 1966 to 1973.
[1] Molloy played his club rugby for University College Galway RFC while he was a medical student there.
Molloy moved to England to further his medical career, where he played his club rugby with the London Irish.
He served as the Ireland team doctor and as the medical advisor to the Irish Rugby Union.
[5] Molloy's important contribution was publicly acknowledged by IRB Chairman Bernard Lapasset, who recognized that Molloy's "achievements, particularly in the key areas of global injury surveillance and the development of cross-sport concussion guidelines, have significantly benefited rugby and the wider sporting family.