Signed as a halfback but now settled at hooker, Sullivan enjoyed a strong second half of the 2006 season operating from the dummy half role from where his electric speed around the ruck can be best employed. Sullivan had been a halfback in his junior days with Wingham Tigers and joined North Sydney Bears - the club for which his father John played in the 1970s - in 1998, making the joint franchise squad when the Bears merged with Manly to form Northern Eagles in 2000. He made his NRL debut in the Eagles' opening season but was recruited by Cronulla Sharks in 2002. It was at the Sharks where first made the switch to hooker, enabling coach Stuart Raper to include Sullivan as well as Test halfback Brett Kimmorley in first grade. Primarily used as an interchange hooker, Sullivan proved to be a dynamic line breaker, rated the best impact player in the NRL in 2004. Born in Taree, New South Wales, Sullivan was one of the most photographed players in the Australian game and was shortlisted as one of the Nivea for Men/Cleo 50 most eligible bachelors in Australia in 2001.