Many did know that Kevin Garnett is one of the trash talkers inside the court, in order to have an advantage towards his opponent guarding him. Sometimes it worked effectively and sometimes it won't but this is one way of making his opponent lost focus and from there he can do the most of his works.
Trash talking is not limited to his opponents instead he trash talk to himself which is a kind of a unique. Probably it can boost his confidence and by that strategy, he could perform well and efficiently inside the hardcourt. There is no denying that Garnett is one of the best players in the NBA and even he got already inducted as a hall of fame.