[1][2][3][4] In 2019, Sonsie made his NAB League debut, playing top level junior football for the Eastern Ranges at age 16, including in the side's grand final loss.
[5][7] During the year he played junior representative football with the Eastern Ranges, top level exhibition games for the AFL Academy side and made his VFL debut for Box Hill where he starred with 24 disposals and two goals.
[2][8] Despite occasional starring performances, Sonsie's draft ranking progressively fell over the course of the season, as pundits considered his output uneven and inconsistent.
[9][10] Across his junior career, Sonsie was lauded for his ability to play inside and outside of midfield stoppages and his disposal accuracy.
[17] In Round 22 of the 2023 VFL season he was suspended for three weeks after violently punching North Melbourne's Tom Cappellari in the head.