Devenney played senior football for Donegal despite not having played underage. His debut against Cork in the National Football League quarter-final at Croke Park in March 1998 was nothing short of sensational: he scored 2–2. Declan Bonner gave Devenney his championship debut in 1998. He played in his first Ulster Senior Football Championship final later that year, and though he lost, he received the man of the match award.
