I am a Michigan fan, and I saw every game David Long played in college. Despite that fact, I didn't see much of him, because teams didn't throw at him often. He had more pass break-ups than catches allowed.
This I can tell you:
1. Despite his short area quickness, athleticism is not his calling card. This makes technique and situational awareness vital.
2. He played, almost exclusively, press coverage as a Wolverine, and I don't recall the Rams running much press.
Those 2 factors make for a steeper learning curve, if he's not primarily playing press. I am reluctantly hopeful.