From last night's PBC Blog Liveblog:
"9:38: NEWS UPDATE: The late-July injection into the left knee of first baseman Steve Pearce didn't work, so he is scheduled for surgery by team doctor Patrick DeMeo on Wednesday."
I assume this means he's done for the year.
UPDATE (8/4): Out for 4 months. So that means he can start getting back into shape at the beginning of December. Too late for winter ball? I'm not actually sure there's anything for him to do other than get back in shape and revive his swing, so maybe minicamp and an early arrival at ST would suffice.