For the Hawks/Nets pick, depending where it is, I'd look at Mitch McGary if he enters the draft. He's out this year due to back surgery, but if he were healthy, he'd be in the 7-15 range of the draft, if that doesn't sound familiar. He's a little closer to being a true center than Jared Sullinger (a couple inches taller and a little more agile, although he's still not a true 7-footer 6'10"-6'11", compared to Sully's 6'9"). He's a good overall rebounder/great offensive rebounder, and has the best outlet passing I've seen in college since Kevin Love (although Kevin Love was the best outlet passer I've seen ever. I don't get to watch Minnesota play -- does he still do that? I used to stay up late just to see him grab a rebound and pass it to a streaking Aaron Afflalo beyond mid-court in one motion. It was a thing of beauty). Anyway, McGary isn't Love when it comes to outlet passing, but it's a real skill that doesn't show up on box scores, since it doesn't generally lead to assists. He's also a very good passer from the high post, and is elite at stealing the ball, especially for a big. His free throw shooting is mediocre, but improved this year before he got hurt, and he isn't as skilled at scoring as Sully.
The thing he needs to work on most is defensive positioning. He's got the physical ability to play great defense, as indicated by his steals, blocks, and rebounds, but he's very aggressive, and susceptible to falling for the first move a player makes, or trying to jump a passing lane and not being able to get back in time. I think some of that can be fixed, as he gains more experience against players who have multiple moves down low, which you never see in high school, and don't see every night in college. Some of that you don't want to fix, as his aggression/energy is part of what makes him special. But it's where he needs to improve the most, and what will keep him on the bench in the NBA (aside from health), if he doesn't.
But if his back checks out to the Celtics doctors at the combine, he's worth picking. If the Atlanta/Brooklyn pick is in the teens, he might be worth trading down for, as I don't see him going earlier than 20.