1) Role grading is critical to Belichick. Otherwiase, we would have drafted many more linebackers early in the last few years. Some here might have thought Matthews and Laurinitis were more valuable than Chung.
2) There must be analysis of other teams and where the player is likely to be drafted. On the approach considered. We could have been sitting at 23 and chosen the top player on our board, even if he were a mid-second rounder. Bleichick does much better in his approach. Consider that Butler and Vollmer were likely very, very high on our board at 23 and 26.
3) Potential trades down and up (and out) are critical parts of Belichick's strategy, not so much for most other teams.
4) Need does play a part. For example, we wouldn't draft a quarterback because he was at the top of our board. There are several ways to accomodate need. One is to remove certain position for certain rounds (e.g. no quarteback before the 3rd). Another is to add points in evaluating positions of need, thus moving up certain players, and moving others down.
5) Character issues must affect draftability. To use an extreme, a player in jail until July for drug seelling will obviously see his draft ranking change compared with someone with no character issues.
6) Finally, certain positions are inherently more risky in the draft. One can automatically reduce the "value" of positions such as wide receiver, while still picking them later than their initial talent and projection might dictate. Other positions are less risky; for example DL's in the 15-35 range and OL's in the 20-80 range.
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BOTTOM LINE
Drafting should be much more complicated than evaluating college potential and giving them a value.
