Deicmans akakwanisa kupinda mumakwikwi maviri ekushambira kumaOlympics ezhizha ra2004 kuAthens, nekukunda nguva dzekupinda muFINA B-standard dze2:03.77 (200 m mumwe nemumwe) kubva kuFINA World Championships muBarcelona uye 4:28.44 (400 m m mumwe nemumwe) kubva kuEuropean Championships
muMadrid. Mumakwikwi emamita mazana mana, Deicmans akakunda Miguel Molina wekuPhilippines kuti aputse chipingamupinyi che4:30 uye akabata nzvimbo yechinomwe pakurova kwechipiri nemasekondi mana, munguva ye4:29.17. Mumakwikwi emamita mazana maviri ega ega, Deicmans akakwikwidza nevamwe vanoshambira vanomwe pakupisa kwechina, kusanganisira vaimbove maOlympics kaviri Jeremy Knowles weBahamas naIoannis Kokkodis weGreece. Akakwira kunzvimbo yechishanu ne0.39 yechipiri kumashure kweBarbados Bradley Ally, achiputsa rekodhi reLatvia re2:03.68. Deicmans akakundikana kuenda kumasemifinal, sezvo akaisa makumi maviri neshanu zvachose mumatanho ekutanga.