My sleeper defender is Isaiah Briscoe from Kentucky, total Bulldog. Ainge guy all the way except he's not very long. Super Strong though, and can penetrate well on offense.
Other than that I'd say Dunn may be the best defender coming out.
Brandon Ingram has been a surprise on defense as well. Coach K said about Ingram he's not low maintenance. He's no maintenance, God I hope we get him.
What I really want to know more about is swing forward defenders or guys that can play three and four.