Antonov akakwanisa kupinda mumakwikwi maviri ekushambira kumaOlympics ezhizha ra2004 kuAthens, nekupfuura nguva dzekupinda dzeFINA B-standard dze23.48 (50 m freestyle) uye 51.65 (100 m freestyle) kubva kuMissouri State Swimming Championships. Mumakwikwi emamita 100 akasununguka
, Antonov akashora vamwe vanoshambira vanomwe pakupisa kwechina, kusanganisira vakwikwidzi veOlympic kaviri George Gleason weVirgin Islands naAllen Ong weMalaysia. Akapedzisa munda kunzvimbo yekupedzisira uye makumi mashanu nemaviri akazara ne0.29 yechipiri kumashure Ong mu52.33. Muchiitiko chake chechipiri, 50 m freestyle, Antonov akaenzana nenzvimbo yake kubva pakutanga kwake mangwanani e prelims. Achishambira mumakwikwi mashanu, akabata Örn Arnarson weIceland kuti atore nzvimbo yechitanhatu ne0.17 yechipiri, kunze kwenguva yake yekupinda ye23.67.