I think he'll easily come back defensively because he doesn't rely on his arms to play defense, his biggest asset is his ability to move his feet to stay in front of his opponant. A guy like Rondo who relies more on getting steals would have more of a tough time on defense.
Where i think he'll struggle is offensively, it's gonna be tough for him to take that next step forward in year 3 when he's rehabbing to start the season.
Just think, this kid STILL hasn't had a full training camp. 
i agree. even playing injured last year bradley's defense was incredible. where he dropped off was his shooting. i noticed he suddenly could not make shots he had been making. i thought maybe he tired, but then i heard that he was injured.
the problem for his offense is that surgery really takes 1 year to recover fully. even though the area having surgery is "repaired" the body has undergone a lot of stress and trauma. a year after surgery is when you can safely say someone has probably "recovered."
so what does this mean for bradley?
one, still great defense next year. but he may tire or not be able to play 35 minutes a game as the same level. the last part is just a guess by me.
two, his offense will suffer, especially his long range shooting, as it did last year. but with lee and terry on the team the celtics may be able to still generate offense. again, guesses.
i expect bradley to play fewer minutes per game than last year. too bad for the kid. this is the third year for him and each year he has suffered through some sort of injury. i hope he gets and stays healthy.