Orešar's senior career was less successful. Apart from winning two gold medals in the 1987 Summer Universiade (in singles and in mixed doubles with Sabrina Goleš), his biggest singles tournament successes were reaching the finals of Athens and Båstad in 1988 and 1989 respectively. A persistent back injury forced him into early retirement from professional tennis in 1991. His highest ATP ranking was #46 in May 1989.