The tendency here is to downgrade players who either haven't had the chance to show much at the college level, or haven't been a top 10 recruit in HS, or may have been moved to a lesser role by a superstar. I think what I would recommend is that you look at the skills and/or physical attributes displayed at each level, and decide does that skill translate.
Clingan - 7'2" with incredible reach, soft hands and touch, and teachable. So he didn't play high level AAU ball, so what?
Hurley has recruited these last two classes with skills/attributes that will translate. I have confidence that Ball, Stewart, Ross, and even Singare may each be contributors next year if they put in the work and trust the coaching. There's a lot there in each of those guys to commend. The first two I think are ready to make the jump. The second two less so, but if Ross gains strength and can reliably shoot and Singare gets the attention and coaching that raw post guys need they both might surprise.
I think we know what Nowell can do, the only question on him is how early can he be a major plus and play significant minutes. I agree with
@mauconnfan that Abraham showed a lot the couple of times I saw him, including athleticism and toughness on D and a nice jump shot out to the line, with touch. I bet he's a significant contributor by mid-season, particularly if Karaban exits.