People can argue all day whether it's smart or not to trade for Matt Cassell. But only one team has to think it's smart for it to happen. In this post I'm going to lay out what I think the value of that trade should be for the Patriots.
The most recent trade for a starting QB was when the Texans traded for Matt Schaub. At the time, Schaub had only started 2 games for the Falcons. The terms of the trade were these:
Falcons give up #10 pick in first round
Texans give up #8 pick in first round
Texans give up # 8 pick in second round
Texans give up 2nd round pick in the following year.
To determine the total value of the trade I'll use the standard NFL draft value chart, found here: http://www.degnan.org/dolphins/draftvaluechart.htm
The falcons gave up the 10th pick (1300 pts) for the 8th pick (1500 pts) for a net gain of 200 pts.
They got Houston's 2nd round pick (510 pts)
They got Houston's 2nd rounder the next year, which is usually discounted by one round since it's a year later. A mid 3rd rounder has a value of about 200 pts.
That's a total of 910 points. 910 points is roughly equal to the 20th pick in the first round (900 pts).
As I mentioned, Schaub had started 2 games at the time of the trade. Cassell played an entire season at a solid level. His value is clearly higher than Schaub's was at the time of the Atlanta-Houston trade.
So the trade value for Cassell should be somewhere above 900 points -- how far above depends on how much better you think Cassell is than Schaub was after 2 starts.
Since that's a tough comparison to make, let's think about it this way. What if Brady didn't get hurt until the end of the 14th game, then Cassell came on and only started 2 games, playing pretty well and showing some promise. Now compare that to watching him over 16 games. How much more sure are you that Cassell is the real deal having seen 16 games than if he'd only played 2?
I'd argue that the Cassell who showed consistency over 16 games is worth significantly more than the one who only played 2. I'd give an extra second rounder for the guy who showed it over 16 games.
A mid 2nd round pick is worth 400 points. To me, that means Cassell's value is about 1300 points. That's equal to the 10th pick in the draft.
But assuming that you buy the argument that Cassell is worth more than Schaub was at the time of the trade, Cassell would be worth at least the 19th pick, and possibly as high as the 10th. So depending on the trading partner and how they value Cassell, you're looking at a mid 1st round pick somewhere between 10 and 19, probably closer to the 10 than the 19.
When you look at this trade value figure, it helps put in perspective possible trading partners. Start with 'who needs a QB?' Detroit, KC, SF (maybe), Buffalo, Jets, Chicago, Tampa (maybe), Minnesota. Not all of them have the same need, but there's at least the potential.
Off the top, eliminate the Jets. Can't see that happening. SF and Buffalo are in a good position to trade at the #10 and #11 spots. It could be a straight 1 for 1 swap, the pick for Cassell. Essentially Cassell becomes their first round pick.
For Chicago and Tampa it's tougher with the #18 and #19 picks respectively. Picks are worth 950 and 925. If you stick to 1200-1300 as the value, they'd likely have to give up their 1st AND 2nd round picks, maybe getting a 4th or 5th rounder back from the Pats. The Vikes, who would seem to benefit a lot from the trade since they have a lot of pieces in place, have the 22nd pick, worth only 850 points. They'd be looking at giving up their 1st and 2nd pick, plus maybe having to throw in a late rounder. That would be tough to pull the trigger on. So in my book, CHI, TB, and MIN are not likely trade partners.
Detroit would seem to have the easiest time since they hold both the 1st and 20th picks. Obviously detroit has many needs, but none bigger than QB. They could draft a QB at #1, then still own the 20th and 33rd picks (#1 in 2nd round). Or they could trade their 20th and 33rd to the Patriots for Cassell and the Patriots 2nd rounder, #58 overall. So your choice is a Rookie QB plus the 20th and 33rd, or Cassell and #1 and #58. The value of #1 and #58 is MUCH higher than 20th and 33rd -- seems like a good trade on both sides.
KC could make an interesting offer and give up the #3 overall pick for Cassell and the Patriots #23 overall pick. I'm not sure the Patriots would look favorably on that trade, but the points work out.
My final point would be that some teams might try to take advantage of Bellichick's known desire to stockpile picks. Instead of offering this year's first rounder, a team could consider giving up a 2nd or 3rd rounder this year, and next year's first round pick. Once you take future years into consideration, pretty much anything becomes possible.