There's nothing not to like about Nelson as a football player. He's a former JUCO star, who showed up at Florida, and immediately become what may be the most complete defensive back in the country, and this season has been a great example of just how versatile and explosive he can be. He's got great size (even better for CB), and is very fast, especially on the field. He shows excellent instincts, with the ability to roam freely in the secondary. When comparing him to other top safeties, the thing that stands out is his playmaking ability. He seems to always be in position to make big plays, either in the passing game, or in run support. Technically he's a very good tackler and overall just rock solid in all his fundamentals.
NEGATIVES
Not much to say here. Yeah, he needs to improve his man coverage, and at times it appears that he's working more of his athletic ability, than anything, but overall, there's little in the way of shortcomings in Nelson's game. He hasn't shown a lot in terms of his blitzing, but that's not to say he can't, and he may not be able to make the move to CB, as some have suggested.
FINAL WORD
Best DB in the draft, period. LaRon Landry has been the default best safety in the country, going into the season, but Nelson's explosive playmaking ability, and great combination of measurables and just plain old football skills, makes him an enticing package for a team looking for either an elite ball hawk of a FS, or even as a cornerback. There's nothing that Nelson doesn't do great, and you watch him play, and see he's still got a ton of potential, to be even better.