I'd say what PFF does a good job of is it tells you the strengths and the weaknesses of a player in terms of results. I find that useful, gives me a good foundation for a player. What it doesn't tell you is why someone is bad at something and if it's correctable. For example, if Shelley was weak, a poor athlete or just not very flexible I'd understand that some of those things aren't fixable and he's going to struggle in protection. Now you can look at something like this:
http://mockdraftable.com/player/843/ and see that he's definitely a solid athlete. Doesn't have great length but he has good lateral mobility which would lead you to believe he's a better fit in a zone scheme where he seals guys with angles and is on the move more and also that he has good enough lateral mobility to protect effectively and get in front of defenders. Maybe he'll never be great at it because of his length, but he has the movement skills to be successful at it. He's also 10 pounds heavier than his combine measurements so one can assume in an NFL training program he's stronger than when he came in, especially considering a small school program likely doesn't have the program an SEC school has for example. So then I watch him, the athleticism shows, especially when he's out in space. So he's a good pulling guard. I watch him in pass pro, and he simply looks lazy and drops his hands a lot and has an inconsistent punch. These things are correctable, they are technique based and that's Benton's calling card. This is just an example of how I'd look at a guy and why I think he can be a plus player on our OL and not nearly the detriment as a pass blocker as people fear. In addition we are drawing these conclusions on limited sample sizes. He's playing inconsistently and getting flipped between LG and RG with regularity. You can also say playing next to Pouncey is an upgrade over Harvey Dahl.
