Career
Kaestner idolized Peter Aerts and began training in kickboxing at the age of 10. As a result of his victory Kaestner would qualify for the K-1 World MAX 2009 Final 16, losing by decision to eventual runner up Andy Souwer. Kaestner"s performance against Souwer would lead to him being invited to the K-1 World MAX 2009 Final 8 as a reservist, although he would lose his bout to local fighter Yasuhiro Kido.
Despite this recent run of good form Kaestner was not re-invited back to the K-1 Max final in 2010.