Ignore my post above because I would take this trade no matter what, because you are gaining a pitching ace and I doubt you start 5 outfielders in your league. If you do start 5 then I would take this and maybe get a good FA to fill Bruce's spot. Even after this trade your outfield is still solid and you pitching rotation gets better
HUGE VALUE FOR BRUCE! This is a classic example of an owner falling in love with recent stats. That same owner if he were a Bruce owner a month ago probably would have dropped him. Bruce will have his hot and cold streaks. There's a reason Lester was being drafted in the top 3 rounds prior to the season while Bruce was a 6th rounder.
Your OF will be fine without Bruce and your pitching will surely be helped with the ace of the surging Red Sox included.