Korica was born in
Kutina to a family of six children. At the age of thirteen he suffered a serious leg injury from a freak accident for which he was immediately sent to the hospital. After his condition deteriorated, there was a possibility that he would have to spend the rest of his life in a wheel chair. After being sent to another emergency care center near
Opatija, he began to recover. Korica was recommended by his doctors not to pursue a career in athletics. His idol growing up was
Franjo Mihalić. Korica's village had no track on which he could practice, so Korica often ran in the forest, many times barefoot. At the time,
long-distance running was not a well-known occupation in Yugoslavia, and the villagers often looked at Korica as though he was crazy. One neighbor, assuming that Korica spent more time running than helping his parents, allegedly threatened if he ran on his property "with those nails on his shoes" (a reference to
track spikes), that he would attack Korica with a
hoe. ==Running career==