There is no nice way to put this, but the Red Sox defense has been atrocious this year. They rank 29th in DER. No team ranked that badly has ever managed to win the World Series. They have been very lucky that Lester has decided to K every batter that he faces, otherwise the holes would be a lot more apparent, Looking at Smoltz .390 BABIP, along with Penny's .326 BABIP, maybe they are still in Boston if the defense is as good as it was last year? The numbers are troubling:
UZR
Ellsbury - (-)14.5, probably due to his belief that running the other way when the ball is hit is the best way to catch it.
Lowell - (-)11.4, he's hasn't been improving, he's merely slowed the rate of regression.
Bay - (-)17.1
Youkilis 3B - (-)4.0
They don't have Varitek, but the fact that he's caught 13.6% (????) of all SBA's makes me believe that he has at least cost them ten runs.
Counting the other negative contributions from Green, and Lugo. The Red Sox have lost about five or six wins, solely due to the defense.
Whatever happens this year, the Red Sox need to overhaul their defense.