[1] In 2014, Petrušev, already over 2.00 meters in height, who had just completed the seventh grade of primary school in Serbia, signed for the youth system of Spanish club Saski Baskonia (Laboral Kutxa).

[2] In summer 2015, the youngster was picked by coach Vladimir Đokić for the Serbia under-16 national team ahead of the 2015 FIBA Europe Under-16 Championship in Kaunas.

[4] Not keen on stopping his secondary education as part of turning professional, Petrušev began looking for a way to continue his schooling while simultaneously pursuing basketball.

[5] Arriving in Connecticut with a foot injury he had picked up at the European under-16 Championship, Petrušev missed the majority of the season, watching the games from the bench and reportedly being disappointed with the style of basketball played at Avon, specifically its run-and-gun nature and disorganized structure.

[2] Once he finally got on the court, though, he quickly adapted to the different style of play, eventually growing to appreciate its faster pace, focus on athleticism as well as being able to stretch the floor, shoot the three, and have the ball in his hands more, none of which he had been exposed to at Baskonia or Serbia under-16 national team.

[7] Playing on a roster led by the number 1 prospect in the country RJ Barrett as well as top recruits Andrew Nembhard and Michael Devoe, Petrušev immediately gained the trust of the team's head coach Kevin Boyle who envisioned the 6' 11" (2.11 m) Serbian as a modern big (power forward or center) who could shoot threes and set himself apart as an inside-outside player.

[9][10] Sources: As a freshman, Petrušev averaged 6.5 points and 2.7 rebounds per game and was named to the West Coast Conference (WCC) All-Freshman Team.

[23][24] On August 9, 2021, he made his debut in the Summer League in a 95–73 win against the Dallas Mavericks in which he posted 5 points, 4 rebounds, and 3 blocks in 19 minutes.

[25][26][27] On August 17, 2021, Petrušev signed a one-year contract with reigning EuroLeague champions Anadolu Efes of the Turkish Super League.

[30] He had a few more solid outings during the first half of the season that saw the defending champions Efes struggle with a 0–4 start before finally recording a win in week 5 at home to the Russian club UNICS.

The team's struggles continued the rest of fall 2021 with a disappointing 9–9 record at the end of December 2021 just past the halfway point of the regular season.

[31] After not getting a single minute of action in the playoffs quarterfinal best-of-five series versus Olimpia Milano, Petrušev also had no playing time at the Final Four in Belgrade as Efes successfully defended their EuroLeague title.

After answering the Serbian national team call-up for two qualification games as part of the team's World Cup third qualification window in late June and early July 2022 (and appearing only in the first game away at Latvia with no points and 10 rebounds),[32] Petrušev joined the Philadelphia 76ers in its Summer League participation in Las Vegas for the second year running later that month.

[43] Petrušev made not only his NBA debut, but also played in what became his only game with the 76ers on October 29, 2023, grabbing only one rebound in two minutes and 41 seconds of action that resulted in a 126–98 blowout win over the Portland Trail Blazers.

[45] The Clippers then traded him to the Sacramento Kings on 3 November for the draft rights of his fellow Serbian and 2022–23 season teammate Luka Mitrović.

On October 23, 2024, Petrušev was loaned back to Crvena zvezda for the rest of the season in order to alleviate the logjam in the frontcourt of Olympiacos after the returns of the injured Moustapha Fall and Nikola Milutinov.