O'Sullivan played four years of college soccer; one year at Eastern Florida State College in 2013 before transferring to Palm Beach Atlantic University in 2014.
[2] During his time at college, O'Sullivan played with Premier Development League sides Orlando City U-23 and South Florida Surf.
[3] O'Sullivan signed with NASL club Jacksonville Armada FC on February 14, 2017[4] He made his league debut for the club on May 6, 2017, coming on as an 87th-minute substitute for J. C. Banks in a 1–1 draw with the New York Cosmos.
[6] He made his league debut for the club on May 25, 2019, coming on for Jad Arslan in the 75th minute of a 0–0 draw with Lansing Ignite FC.
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