NK Rudar
Šišić began his professional footballing career in Slovenia with NK Rudar Velenje in 2001. In 2003, Šišić signed with Ilisiakos F.C. in Greece. After one season with Ilisiakos, Šišić's career continued to progress in Greece. Šišić moved on to Larissa and then Levadiakos (with a short loan spell at Iraklis, and, after a strong start to the 2007–08 season with Levadiakos, Greece's most successful club, Olympiacos swooped for the Slovenian winger.