Pokusevski was born December 26, 2001in Belgrade, Serbia (formerly Yugoslavia). He grew up in Novi Sad, where he began playing basketball for local teams. He broke onto the scene as a youth player for Olympiacos Pireaus, a Greek club. Pokusevski has dual-citizenship in Servia and Greece. At age 17, Pokusevski was promoted to the Olympiacos senior team, becoming the youngest EuroLeague player in club history. From there, his stock rose and he caught the attention of more NBA scouts. In 2017, he participated in the Jordan Brand Classic camp. He also played in the Basketball Without Borders Europe camp in 2018 and the NBA All-Star Basketball Without Borders Global Camp in 2019. Pokusevski played for the Serbian national under-17 team and the under-18 team in back-to-back seasons. Pokusevski began his professional career in Munich, Germany with Olympiacos U18, playing three games in a tournament. He averaged 10.0 points, 4.7 rebounds, 2.3 assists, 2.0 steals and 1.0 blocks in 23.0 minutes. The following season, in 2018-19, he played for both the U18 team and the parent club for Olympiacos -- four games with the former and two games with the latter. With the U18 team, he averaged 15.8 points, 7.0 rebounds, 3.5 blocks, 2.5 assists and 2.3 steals in 26.3 minutes. The next season, in 2019-20, he appeared in 11 games with Olympiacos B, where he averaged 10.8 points, 7.9 rebounds, 3.1 assists, 1.8 blocks and 1.3 steals in 23.1 minutes. He also played one game with the parent club. Arguably the best game of his pro career before the NBA was during the U18 Euro Championship A, playing for Serbia against Germany. In the win on July 27, 2019, Pokusevski posted 16 points (5-13 FG, 2-7 3Pt, 4-7 FT), 13 rebounds, seven blocks, five assists and three steals in 29 minutes.