As a 16-year-old, Kirby went to England to join Premier League club Aston Villa. He spent four years with the club without making a first-team appearance, and returned to his native Waterford. He signed for League of Ireland Premier Division club Waterford United in 1999, and two-and-a-half years later moved on to Longford Town. During his six seasons with Longford, Kirby won two FAI Cups, in 2003 and 2004, and the 2004 League of Ireland Cup, and was nominated for the 2003 PFAI Players' Player of the Year award.