I remember when I was covering prospects for a crappy little website and I went and saw Giolito in person 3 times. The command is a huge issue but his changeup isn't good and that's the bigger issue. I had major disagreements with another member of my team because he wanted to list him as the #1 prospect in baseball...ahead of Bryant, Buxton, Correa etc.
If Giolito doesn't develop a changeup he'll end up in the bullpen where he'll probably be elite. I would try like hell to trade a $15 Giolito but I won't own a single share of him next year because I would be a buyer at about $3.