Rob Neyer speculated a 60% probability of Boston winning. That seems pretty plausible from a statistical point of view. Boston has better hitting and much better pitching. I've seen some nonsense about how Colorado's pitching was great after the All-Star break, but that is a cherry-picked stat. Maybe it was great because they played more road games and against lesser competition? Their line-up stands up pretty well side-by-side to the Red Sox, but their pitching is not even close.
So... yeah Red Sox in 5 seems appealing. That would have Beckett getting a chance to clinch, though it would be at Coors Field.