 He challenged Mitchell later in the year and in a fight in which Siaca was down in the first and Mitchell was down in the 12th, Siaca lost a split decision.In 2004 Siaca was able to capture a belt, winning the WBA Super Middleweight Title in an upset split decision victory over Anthony Mundine.He lost the title in his first defense to Mikkel Kessler, after Siaca remained in his corner after round 7.