Before moving to DME Academy, Avdejev played at Layton Christian Academy in the United States. While at Layton Christian, he received a basketball scholarship offer from Southern Utah, announced in a post shared jointly by the school and Avdejev. On September 10, 2025, Layton Christian also announced a UNLV scholarship offer in a post shared with him. FIBA's August 2026 review selected him among the U18 EuroBasket's standout players and reported his move to DME for the following school season.
He averaged 10.9 points, 10.3 rebounds and 2.1 blocks for Estonia at the 2026 U18 European championship, helping the team finish tenth. These figures describe his national-team summer, not his DME season.
In 2024, he helped Estonia win U16 EuroBasket Division B and earned the tournament MVP award and an All-Star Five selection. He averaged 12.7 points and 10.4 rebounds, while leading the tournament with 2.1 blocks per game.