Slavica moved to Zagreb, as a 10-year-old, to play for Cibona's youth teams,[1] and he spent one season on loan at KK Zrinjevac.

Following the conclusion of his loan spell at Zrinjevac, during the 2013–14 season, Slavica returned to his parent club of Cibona, and he became a regular on the club's senior men's team, Cibona Zagreb, seeing action in the Croatian League, the ABA League, and the lower-tier level European-wide competitions of the FIBA Europe Cup,[2] and the Basketball Champions League.

[8] In January, 2020, Slavica signed with Adria Oil Škrljevo of the Croatian League.

[10] Slavica played for the Croatian under-16 junior national team at the 2013 FIBA Europe Under-16 Championship.

He helped the Croatian under-18 junior national team win the bronze medal at the 2014 FIBA Europe Under-18 Championship.