On 23 February 2003, Walsh made his first appearance for the Waterford senior hurling team when he lined out at midfield in a 4-11 to 0-12 defeat by Kilkenny in the National League. He made his first appearance in the Munster Championship on 11 May when he came on as a substitute for Tony Browne in a 2-26 to 1-12 defeat of Kerry. on 29 June, Walsh was introduced as a 67th-minute substitute for Eoin McGrath in Waterford's 3-16 to 3-12 Munster Championship final defeat by Cork.