Beginning his career with Cardiff City at the age of nine, Tommy made his debut for City against Northampton Town in the League Cup back in the 2008/09 season.
Following several appearances for Cardiff in Cup competitions, the Rhondda-born player made two separate loan spells at both Newport County AFC and Port Vale at Sky Bet League Two level.
The box-to-box midfielder was named as 2015 Welsh Young Player of the Year by the Football Association of Wales on the 5th of October and scored his first professional goal for Newport County AFC just nineteen days later in a 4-1 win over Bristol Rovers.
After a successful trial at Colchester United, O’Sullivan signed permanent terms with The U’s ahead of the 2016/17 season. This was the first permanent transfer of his career, away from boyhood club Cardiff City.
After being further frustrated with lack of first team football at Colchester however, O’Sullivan joined National League club Torquay United on loan in January 2018.
Now 23, O’Sullivan joined the Bulls after ending his loan spell with Torquay and being released by Colchester following a successful trial at Edgar Street.
Tommy also has an impressive history of youth international football under his belt.
The midfielder has scored three goals in 15 Wales Under-21 appearances and also has a history at lower age-groups, earning nine Under-17 caps and scoring once, as well as playing for the Under-19s seven times, firing in six goals from midfield.