 O'Sullivan started the 2003 season by playing in all 7 of Kerry's games, mostly in the full back line.He started his first championship games since the previous years Munster semi final loss to Cork, when he lined outed at left corner back against Tipperary, in a game Kerry ran out winners on a 0-025 to 1-10 scoreline.This set up a Munster final with Limerick, who had pulled off a shocked result with a 10 pint win over Cork in the semi final.