5. Bismack Biyombo
Sure, we don't often consider projected lottery picks to be sleepers. Biyombo is exceptional in so many other ways, though, that we should make another exception here.
If Biyombo had a longer resume or had handled his pre-draft run-up better, he is a player who should be talked about as a top five selection. Biyombo is arguably the best defensive prospect in the draft. His combination of absurd length, ability to contest shots intelligently, his ability to play one-on-one in the post and roam as an active help side defender, and his ferocious desire for cleaning the glass make him elite on that end of the floor. With that package, who cares about his out of nowhere backstory (raised in the Democratic Republic of Congo, limited professional career in Spain).
Unfortunately, he's now working to prevent a draft day slide after tanking a workout in Europe and laying low for almost the entire pre-draft process. Biyombo is now projected outside of the top 10 and potentially outside of the lottery, which would be borderline criminal given his upside and physical tools.
There's no question that it will take guts to draft him given the red flags about his age (he could be much older than he says he is) and his meteoric rise to the first round following the 2011 Nike Hoop Summit. But this is a player about whom people will almost certainly look back in five years and say, "how in the heck did they pass on that guy in that draft?"