Raw counting/rate stats don't tell the whole story. He still walked, still didn't strike out, and as Boxcar mentioned, his babip took a nosedive which may just be SSS noise. His power output dipped, but I don't think Smoak is in danger of putting up a .140 ISO for any meaningful length if time.
If I recall correctly he missed some games towards the end of August with a leg injury, and probably played through it the rest of the year which could be partially to blame.