He was the 31st pick, he's not a bust. I think both RJ and Mickey have NBA skills that other teams saw but the reason they went that low was because it will take time to get the rest of their game to catch up.
For Mickey, his contract is designed to get us his bird's rights before he can become a FA. To me that's an indication that we want to have him around for long enough to develop him into the finished product. If he becomes a rotation guy then that's a win for us. To do that he needs to improve his range and learn the defensive schemes we run. At that point he is a shot blocker, a PnR defender and has range. He'd be a very decent 4th big in our system alongside Horford, KO and Amir. I suppose he'd compete with Jerebko for minutes at that point