following a 2-14 to 0-13 defeat of Waterford in the final. In 1999 O'Sullivan was switched to the full-back position for the championship. On 4 July, he won his first Munster Championship medal after a 1-15 to 0-14 defeat of reigning champions Clare. On 11 September, O'Sullivan was at full-back for the All-Ireland final against Kilkenny which Cork won by 0-12 to 0-11. He was later honoured with his first All-Star award, while he was also named as the Young Hurler of the Year. On 3 July 2000, O'Sullivan lined out in his second Munster final. He was described as "majestic" at full-back and was instrumental in saving a Tommy Dunne penalty in the 0-23 to 3-12 defeat of Tipperary. O'Sullivan ended the year with a second successive All-Star. On 5 May 2002, O'Sullivan scored a 65-metre free in Cork's 2-15 to 2-14 defeat by Kilkenny in the National League final. Later that season he became a dual player when he was selected for the Cork Gaelic football team. He made his first appearance at right corner-forward on 16 June in an 0-08 apiece draw with Kerry in the Munster Championship. O'Sullivan won a Munster Championship medal on 21 July after being introduced as a substitute in Cork's 1-23 to 0-07 defeat of Tipperary in the final replay. On 29 November, O'Sullivan and six of his teammates from the Cork hurling panel held a press conference at the Imperial Hotel to announce that all 30 members of the panel were withdrawing their services from the county in the hope of better treatment from the county board. He remained a high-profile representative at the negotiations over the following two weeks and was one of five Cork senior football representatives who agreed to a settlement with the county board on 13 December. O'Sullivan lined out in his third Munster final on 29 June 2003. As full-back he marked John Mullane but was substituted with Mark Prendergast after fifteen minutes. Cork won the game by 3-16 to 3-12 with O'Sullivan winning his third Munster Championship medal. On 14 September, he was at full-back for Cork's 1-14 to 1-11 All-Ireland final defeat by Kilkenny. O'Sullivan ended the season by being nominated for an All-Star, but lost out to Kilkenny's Noel Hickey for the full-back berth. On 27 June 2004, O'Sullivan lost his first Munster final when Waterford defeated Cork by 3-16 to 1-21. In