Chuckie is the Knight
I just finished watching it the first time, but it amazed me how much SLJ's chess advice related to Fresh's struggles.
Right after he loses his little girlfriend, Jackson talks about guys who rely on and protect their queen too much, and that's how they get beat. AKA If you want to be the man, don't fall in love--that's how they could hurt you.
In the same scene, Jackson says yea you like your knight and his moves(Chuckie) and you want to protect him, but you gotta use him to get to my king, like any other piece.
So did Fresh use Chuckie? He knew Chuckie would mouth off to everyone and Corky would then come after them. Hence why he switched the drugs--he knew Corky was going to mug him. So did he sacrifice his friend to get the King? Only problem is it makes Fresh less likable but all the more impressive.