The Ricky Williams case underscores the notion that the NFL draft is nothing more than a crapshooot. Ricky won the Heisman. He was a man among boys in college. I don't think anyone doubted his physical ability to make it in the NFL. There were questions about his personality, but often, those elements can be overcome.
New Orleans gave up their whole draft to get him. Ditka took pretty good care of the star, though he was always different (like wearing his helmet during interviews). Miami gave up too much to get him. And Dave took decent care of him early in his time in Miami, but then the stress of the job forced his hand, and Williams was exposed as having social issues that were magnified.
...and so, in all, there were 11 draft choices expended on a guy who had the goods to play at this level, but who flaked out and proved he didn't have what it took psychologically (though I'm not psychologist, and don't know him) to do so.
In that respect, will Brady Quinn, Tedd Ginn, jr, or John Beck be any good as pros? Who knows?