In Walston, you are banking on projectability because he is loaded up with it. At 6’4 and 172, he has tons of room on his frame to add some strength. When you factor in that he is already touching the low 90’s, most scouts think his fastball could be a real weapon for him from the left side as he physically matures. He has really good feel for his breaking ball and an added plus is that he is a prep pitcher that already has a changeup in his arsenal.
The downside here is that you are betting on the future with Walston, not necessarily on his current stuff. His current stuff doesn’t scream first rounder, but if the Diamondbacks are picking him this high....they must feel very confident that he will physically mature and approach his ceiling. It is worth mentioning that he will not be cheap to sign away from his NC State commitment.