Kirby was ever-present during the 2002–03 season, scoring three times as Longford finished fifth. They reached the 2003 League of Ireland Cup Final via a 90th-minute equaliser against Derry City followed by the winner in the last minute of extra time, when Kirby's free kick struck the post and Alan Murphy converted the rebound. St Patrick's Athletic goalkeeper Chris Adamson made "the save of the night" from Kirby towards the end of the final, which Longford lost by a single goal when Barry Ferguson missed a penalty with the last kick of the game. They went one better against the same opponents in the FAI Cup Final. Playing at Lansdowne Road, on a bigger pitch that allowed the wingers more space, Kirby fed Sean Francis to open the scoring, as Longford went on to beat St Pat's 2–0 to win the first senior trophy in their history. His performance over the season earned him a nomination for the PFAI Player of the Year award, but he lost out to Shelbourne's Jason Byrne.