he needs to amp himself up by talking trash, it motivates himself with his team mates and had been doing so for his entire career
I think the whole Melo incident changed KG's game mentally a lot
The fact that he got confronted changed his "tough guy" on the court mentality as he probably doesn't want another confrontation and get called out again
He is a year older and probably his body just took too much off a beating since coming out of HS
It is night and day, as he looked like he was thriving at the C position last season in the play offs and had been reborn when it counted most
Only the few games that he came back in the regular season had a good performance
Lets not forget that he is missing a true PG and penetration to set him up as well