His coach Ante Tešija decided Vlašić would do well in decathlon, describing him as "tall and skinny".

According to Tešija, Vlašić was initially very skeptical regarding his aptitude for the sport, but he was tenacious, loved to train, and the results came quickly.

[1] Vlašić's decathlon personal best of 7659 points, set in İzmir in June 1983,[1] was the Croatian record until July 2021.

In her youth, she tried many athletic events, as well as sports such as tennis, basketball and volleyball, but settled on high jump after consultation with her father.

[8] Joško Vlašić is married to Venera Milin, a physical education teacher and a former cross-country skiing national champion.