I think this is more of a tough call then people realize. Sure Arizona is in bad shape right now, but the Rams may win lets say 28-10, and Bulger throws for 190 yds and 1 TD...because the Rams will run the ball...but the Colts may lose to NE and Manning may get 300 yds in a loss becuase they will be playing catchup...
The weather may be a factor, if the weather isnt, Id start Manning, if it is, then start Bulger.