The Irish U21 player was part of the Republic squad for the World Youth Championships in November 2003. The Academy player made one appearance for the Blues in his first season in the senior squad with a start against TNS in the Uefa Cup qualifier in 2003, but didn't take part in any Premiership games that season. He was loaned to Rochdale for first team experience in mid-March 2004, where he played six games before returning to COMS.
The promising youngster then appeared in the pre-season friendly against Lazio in August 2004. His full home debut came in the Blues 7-1 thrashing of Barnsley in the second round of the Carling Cup the following month. Flood and Shaun Wright-Phillips continually opened up the Barnsley defence with some lovely inter-play before the midfielder scored in the thirty-third minute of the match to cap what he described as a;"memorable day".
After another impressive display in the Carling Cup against Arsenal Flood was drafted into the team against Norwich City for his first league start for City. The 19 year old responded with a man-of-the-match performance, scoring a fabolous volley goal. He also had a shot denied by the post, and throughout the game proved to be a constant threath to the Norwich defence. In the manners of another Irish and City great; Peter Doherty, Flood showed his skills as a dribbler, runner, tackler and goalscorer in his first full Premiership game for the blues.