Born in Sapele, Nigeria, Defiagbon won gold in the welterweight (– 67 kg) division at the 1990 Commonwealth Games. As a light-middleweight, he won a bronze medal in the 1991 All-Africa Games in Cairo. In 1992 in Barcelona at the Summer Olympics he represented Nigeria and was eliminated in the first round of the light middleweight division (7 to 8 against Raúl Márquez).