It is a tough break. However, taking the Pats at 3's at the start of a season in a sport where season ending injuries are a weekly occurance was a major risk not worth taking for anyone. If the Pats had the kind of season many would expect from them, you'd still be able to get them at anywhere between 11/10-5/2, depending on exactly how the season may have gone.
It's not like backing say the Steelers, Giants or Saints in September at 20's plus and then seeing them backed down to 10's or lower once the playoffs start. At that level, the differential is worth taking because the price differential between now and later is likely to be significant. That wasn't going to be the case with the Pats, they were too short to back.
And now that bet is all but a goner. Yes, Cassel may come in and do what Brady did when Bledsoe went out, but you wouldn't want any of the Pats now at 5's would you?
I thought you were talking about the -15 line on game 1. My mistake