Sherlock was in his third and final year of the under-21 grade when he made his first appearance for the Cork senior team on 21 February 1999. He was selected at right corner-back for a 0-14 to 1-09 defeat of Kilkenny in the National Hurling League. Sherlock made his first championship appearance when he was selected at right wing-back on 8 June for Cork's 0-24 to 1-15 Munster Championship defeat of Waterford. 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, Sherlock was again at right wing-back for the All-Ireland final against Kilkenny which Cork won by 0-12 to 0-11.