Karetsas came through the system at his home town club Genk before spending three years at Anderlecht.
[2] He made his professional debut as a fifteen year-old for Jong Genk in the opening game of the 2023-24 season.
[3] When he scored his first professional goal on 1 September 2023, in the Challenger Pro League against RSCA Futures, he became the youngest goalscorer in Belgian pro-league history.
Two weeks later, interim head coach Domenico Olivieri give him a first-team start for the first time for the league match against Royal Antwerp and in the 28th minute, he provided the assist for the only goal of the game, scored by Andi Zeqiri.
[8] Karetsas was selected by the Belgian Under-21s for European qualifiers against Scotland and Hungary in October 2024, coming on as substitute in the latter match for this debut at that level.