The problem with most under the radar players is that they are not like Greg. Sure there are a ton of 3 star football players that are long and skinny, that don't really stand out because they didn't go to camps and don't look physically like a college football player yet. But then they go to college and while they get to a good size and finally learn how to truly play their position, they are not stars and most are just JAGs. You can take 10 each class and more than likely only 1 or 2 will work out and be an impact player. To win championships you can't take those odds.
Just look at the last 10 years of Miami football, we have been living off of these 3 star players that just need a bit of development and will become stars. There have been so many reports by coaches and even Miami reporters saying that we got a steal in a 3 star recruit, that once he gets on campus and adds weight he will be a start. Recently, Robert Knowles and Mike Smith were suppose to be just that. Practically all our DTs from the Al Golden era were that, as well as, the OL since then. The fact of the matter is that you will more than likely get an Larry Hope and Robert Knowles type player than you are to get a Greg or RJ McIntosh.
You could of course blame the evaluations, but lets be honest it is near impossible to accurately judge who will become stars based on potential. It will be near impossible for any coach to be even near 50% accurate on their predictions.
Now some of you will state, "But look at the draft and all these players that go to small schools and were lowly rated," while that is true most of those schools have 84 other players that looked just like him as a recruit, that didn't turn up to do anything.