Kasper made his professional debut for Rögle BK on 21 January 2021, where he played 11 minutes 35 seconds.

He recorded his first NHL point on October 19, 2024, in a game in a 5-2 win over the Nashville Predators, assisting on a goal scored by Vladimir Tarasenko.

[4] He scored his first NHL goal on November 15, 2024, in a game against John Gibson of the Anaheim Ducks that resulted in a 6-4 loss.

[5] Kasper represented Austria at the 2021 World Junior Ice Hockey Championships where he recorded one assist in four games.

Kasper had a role in the Austrian film Harrinator, playing a young hockey player named Robert Begusch.