Mezue nkebi ahịrịokwu a: N'egwuregwu Olimpik nke 2004 e mere n'Atens, Alleyne mere nke ọma n'asọmpi igwu mmiri abụọ. O wepụrụ oge ntinye FINA B nke 51.89 (100 m freestyle) na 1:53.19 (200 m freestyle) site na Pan American Games na Santo Domingo, Dominican Republic. Na 200 m freestyle, Alleyne gbara ndị ọzọ na-egwu mmiri asaa na okpomọkụ nke atọ, gụnyere ndị ibe ya bụ Joshua Ilika Brenner nke Mexico na Giancarlo Zolezzi nke Chile. O meriri Mahrez Mebarek nke Algeria iji were ebe nke atọ na nke iri atọ na anọ n'ozuzu site na 0.11 nke abụọ na 1: 52.89. N'asọmpi nke abụọ ya,
Na 100 m freestyle, Alleyne nọ n'ọkwa nke iri anọ na asatọ n'isi ụtụtụ. Na-egwu mmiri na okpomọkụ nke atọ, Alleyne kwekọrọ na oge ntinye ya nke 51.89 iji chekwaa ebe nke ise n'elu onye obodo Zolezzi bụ Max Schnettler site na 0.02 nke abụọ.