Outside of QB and maybe D Line** there isn't a single unit that wouldn't be improved by a top 10 pick. I don't understand the positional requirements argument, the Patriots have only had one top ten pick (Seymour) and he started in the first year and became a pro bowler. I don't think any draft pick would be expected to start so I don't see why an elite player at any position couldn't come in and become the top reserve and eventual starter.
I think I get where you're coming from. If you see a guy you think can be a game-changing, HOF-type talent, that's never really wasted. But I do think the position is a critical factor. Here's how I think about it...
When you excluded QB and DL, you were presumably thinking 2 things:
1. Those positions are so strong right now that the potential for a meaningful upgrade is minimal and we'd get a bigger impact elsewhere;
2. We have so much money tied up in those positions right now that it would be lousy cap strategy to commit another huge contract to a rookie.
Extending just those 2 arguments, I think you can rule out a number of other positions as well. Take LG anc C. Could you improve on Logan Mankins or Dan Koppen with a top-10 pick? Maybe, if you're lucky. How much would that incremental improvement be worth to you, though? This year's #5 pick signed for 6 years, $62 million. Is the projected degree of upgrade over a pro-bowl caliber guard like Mankins really worth 9% of your salary cap? And with Koppen already pulling in an average of of $5 million/year through 2011, would you really be willing to devote a total of $15 million/year to the center position? I can't imagine it.
Now let's throw in some extra factors. Is the position worth $10 million/year, period? Some positions require rare physical specimens and are hard to find on the FA market. In contrast, I don't think any RG in the league is worth 9% of the salary cap.
How about risk, "projectability" and time-to-impact? That's where WR and ILB run into trouble. WR is the hardest position to project from college to the NFL. It has a high bust rate, and this year BB seemed to give up on drafting WRs altogether and traded 3 picks for veteran receivers instead. ILB is a super-steep learning curve position where the Pats have struck out several times with both vets (Beisel, Brown) and highly regarded rookies (Claridge). I'd be mighty nervous committing #5 money to either position.
At TE the Pats have Watson, Brady and Thomas under contract for next season, and there's no Vernon Davis type in the draft this year anyway. Kenny Phillips at safety is a possibility I guess, and
maybe McFadden. But I really think that the desired combination of value, rarity and impact is concentrated at just three positions: CB, OLB, LT.