Glenmore's run of success to the 1991 All-Ireland Club Championship title saw O'Connor being drafted onto the Kilkenny senior team for the latter stages of the 19901-91 National League. He made his first appearance for the team on 30 June 1991 when he was introduced as a 15th-minute substitute for Liam Walsh in a 2-09 to 0-13 defeat of Wexford in the Leinster Championship. On 21 July 1991, O'Connor broke onto the starting fifteen when he was selected at right corner-back for Kilkenny's Leinster final-meeting with Dublin. He ended the game with his first winners' medal after the 1-13 to 1-11 victory. On 1 September 1991, O'Connor was switched to left wing-back for the All-Ireland final against Tipperary. He ended the game on the losing side after the 1-15 to 0-16 defeat.