[1] He made his professional debut on 26 December 2009, in a Scottish Premier League match against Celtic.

[7] On 4 March 2016, in the season opener against St Patrick's Athletic at Richmond Park, Sullivan made his debut and scored an 83rd-minute header in a 3–1 win.

[8] Despite the great start to his time at Galway United, it was announced on 28 June 2016 that Sullivan had left the club citing travel issues.

He then stopped playing at 28 years old and joined DLR Waves as a coach for their 2020 season.

This biographical article relating to Republic of Ireland association football is a stub.