[16] In 2018, Kotsopoulos played one league match for League1 Ontario side Vaughan Azzurri and scored a hat-trick.

[20] On June 12, 2019, Kotsopoulos made his debut as a substitute in the Canadian Championship against Cavalry FC.

[22][23] In August 2019, Kotsopoulos opted to return to the University of Guelph to finish his final semester.

On March 13, 2021, Kotsopoulos became the first ever player to sign with League1 Ontario expansion side Guelph United.

[30] He led the league in scoring in 2021 with 15 goals in the regular season,[31] and helped the team win the league championship, scoring twice in Guelph's 3-1 victory over Blue Devils FC in the championship final.