I have a theory, and it's merely just that - a theory.
But I talked about it about QBs, and I think it's reasonable for me to apply my theory to other positions, since it's mine, of course.
Why is it that mid-to-late rounders and UDFAs find success in the NFL?
Tom Brady, Tony Romo, Jay Ratliff, Miles Austin, almost ALL of those guys on that O-line comparison?
My QB theory applies mostly to SEC quarterbacks...and I think it applies to the guys that go in the first round too. The majority of them were the biggest, strongest, fastest guy in HS, and in college they were the biggest, strongest, or fastest guy on their team. They got by on their athleticism, and even if their fundamentals were sound, they may feel as if they were so good that they are able to just get drafted, show up, and compete at an NFL level.
We all know the NFL game is CLEARLY different from the college game. I think this is why these guys struggle, and guys out of the 6th or 7th round end up finding success. See, the guys in the 6th and 7th rounds aren't told they're God's gift to quarterbacking, or cornerbacking, or linebacking, or anything else...they have to work for their playing time. They didn't have the best facilities in the nation, or the luxury of playing for a big school. So they get in the NFL, and they have to do things like learn to read defenses EXCEPTIONALLY well (Brady, Romo) or just dig really deep and work ridiculously hard to propel themselves to the starting role (Ratliff).
Even a guy like DeMarcus Ware, although drafted in round 1, still had to prove himself, coming from a smaller school like Troy. He didn't face TOP talent every year, or play against "SEC competition" that the draft experts love to him and haw about all the time.
So...that's my theory. Guys in the later rounds have to work harder, and thus they work harder to stay on top.
But it's just a theory.