There's no effective difference between #33 and #34?
Well, actually there is a difference, one pick.
There could be a player that the Pats want at #34 who goes at #33. I don't recall the Pats ever offering "after you" during the first 200 or so draft picks, for no compensation.
As noted, the Pats could have achieved the exact cap outcome by trading Cassel for the #33, and releasing Vrabel.
Further, after trading Cassel, there was no short-term salary cap imperative to release Vrabel. With $14.6mm in additional space, a further $3mm was not needed this weekend.
If the Patriots were concerned about Vrabel re-uniting in Cleveland with Mangini, they could trade him to any other team, hell, for a 2012 7th round pick or something. Given six months, they probably could have found a partner. It's possible one team valued Cassel more than KC, and maybe another team valued Vrabel more than KC. Or asked him to restructure. Before the trade, I think there were fewer "trade Vrabel" threads than "trade Brady" threads - there was no great clamor to dump Vrabel to save the defense and cap a week ago.
In the past, the Patriots seemed far less concerned about where a player ended and far more about maximizing the value of the return. The Drew Bledsoe trade is a pretty clear example of this approach.
The facts seem to show that the Pats did not maximize value in this deal. You can argue how much value - oh, it really was only a little value that they gave up. But this is a competitive organization in a competitive league. Strange to see this approach.