Date of birth: 18/09/93
A versatile attacking midfielder who can play through the centre or out on either wing, O'Sullivan is another player who has come through the Rovers Academy to be on the fringes of the first team squad.
One of the stars in the Under-18s run to the final of the FA Youth Cup in 2011-12, Dublin-born O'Sullivan made his Rovers debut at the end of 2012-13 as a second half substitute in the final game of the Championship season against Birmingham City.
An injury at the start of the 2013-14 campaign set O'Sullivan back, but he ended the season strongly whilst on loan at Conference side Southport where he scored three goals in 21 appearances for the Sandgrounders.
September 2014 saw the midfielder make a month-long loan move to near neighbours Accrington Stanley. It was quickly extended for the remainder of the year after he enjoyed a sensational debut with two goals and an assist as the League Two side defeated Northampton Town.
A regular on the international stage for the Republic of Ireland, O'Sullivan has been capped up to under-21 level.