Two things about curveballs...if a hitter is pretty sure a curve is coming, it's a lot less effective. The other thing about curve balls...it's not the great curveball that you snap off that gets you in trouble. It's that hanger that rolls up there, thigh high, with a big "hit me" flashing neon sign. Throw one bad one for every good one, and you are likely not a very good pitcher.