I have been trying to figure that out myself. I found some places that listed the Pats as 1 or 2 point favorites, but
according to Vegas Insider the line moved to Buffalo being favored by 1 or 1.5 in most venues just before game time. Perhaps a reaction to a lot of late money coming in on one side? There were
no significant injuries that I found, just C Wendell Ryan and DL Dominique Easley for the Pats.
Buffalo did beat Indy 27-14 the previous week, but the Pats had also defeated Pittsburgh in week one, 28-21. Maybe it was the aura of Rex Ryan making the Bills a trendy pick, or the fact Buffalo had defeated the Patriots 17-9 in the most recent meeting at the end of December. Perhaps it was due to the Pats being on a
1-5 streak against the spread versus AFC East teams, and 2-3-1 ATS overall in their last six games - while Buffalo was viewed as a hot team, going 5-2 straight up and 6-1 ATS in their last seven games.
There is also the possibility of people expecting a letdown by the Pats after an emotional week one, when the Pats beat the Steelers in their banner raising opener and also celebrated the overturn of Brady's deflategate suspension.
For the record the Pats led 37-13 after three quarters, then Buffalo scored three 4th quarter touchdowns to pull within five with 4:16 to play. In the 4th quarter the Pats failed to convert on a 4th-and-1 from the Buffalo 41 that led to the Bills second touchdown of the quarter, and two plays later Brady was strip sacked that immediately led to another TD. The Pats got it back in gear on the next possession, driving to the Buffalo 8 while winding the clock down to 1:18 before settling for a FG, and a 40-32 lead. Logan Ryan picked off a Tyrod Taylor pass intended for Sammie Watkins two plays later to clinch the win.