His semifinal match, against rival Wanderlei Silva, was held on August 28, 2005. Arona surprised everyone when he defeated Silva, who was the PRIDE Middleweight Champion at the time, by decision, handing Silva his first middle weight defeat in PRIDE. Despite Silva's feared striking, Arona put him down with an early leg kick and worked on an extensive ground and pound, taking him down every time the fight got standing in order to continue with the punishment, which lasted until the last minute. After defeating Silva, Arona advanced to finals where he faced rising MMA fighter Maurício "Shogun" Rua, brother of Murilo Rua and Chute Boxe integrant. In a dominant performance, Rua reversed a takedown from Arona and got the advantage, opening his hips to catch Arona in an omoplata. Instead of submitting Arona, Rua used the advantage to get top position, then after a missed stomp, knocked Arona out with hammerfists to the face.