He signed for Shamrock Rovers under Seán Thomas at the tail end of the 1975/76 season.
He made his debut on the 5th of September in a FAI League Cup tie against Home Farm and his first goal came in the next game at Oriel Park.
He won the League of Ireland Cup and made 4 appearances in European competition while at Glenmalure Park.
That season he was the first recipient of the Shamrock Rovers Player of the Year award Shamrock Rovers F.C.#Player of the Year In May 1980 Gaffney guested for Waterford United on a tour of the US [1] He signed for University College Dublin in August 1983 [2] He won the FAI Cup in a shock win over his previous club in May 1984 and played in the UEFA Cup Winners Cup against Everton.
Under Brian Kerr he won the League Championship in 1990 as well as playing in the following season's European Cup.