Dević was born in Donje Biljane, a small village in Ravni Kotari. Growing up in Kninska Krajina, he first specialized in the 1500 metres. He became one of the most competitive middle-distance track runners in all of SR Croatia and ran at the 1987 Summer Universiade in Zagreb. When Yugoslavia began to break up, he moved briefly to Sarajevo, but soon took refuge in Belgrade while his parents moved to live in the United States. Being without his parents or any close relatives in Belgrade, he was invited by Goran Raičević and his wife Jelena to live with them. He formed a very close friendship with Goran, and their training together lasted up to the time when Dević ran the men's marathon at the 1996 Summer Olympics, finishing in 49th place of 111 finishers with a time of 2:21:22. He finished in seventh place at the 1997 Belgrade Marathon in a time of 2:16:01.