Yaxel Lendeborg, Morez Johnson and Cameron Carr is probably my short list of guys right now.
Yaxel is old, but not a late brakeout guy which are the real ones you need to worry about. I don't think he has any star equity, but could he be a bigger PJ Washington with some sprinklings of Aaron Gordon? I think that's reasonable to project.
Morez is a junk yard dog. Not quite as physically talented as Al Horford, but close and I buy the jumper and the feet on defense to project some positional versatility to play alongside and back up DC.
Cam Carr is a super smooth, long wing with 3 level scoring ability and the tools to make plays defensively even if the his strength and play to play defense isn't where'd you like it to be. His tough shot making combined with his tools give him some real upside but has enough secondary skills to hit as positive player even if he doesn't reach it.