Kemp was inconsistent and has never been good offensively for s significant stretch of time since his huge year.
In my mind, I think Kemp with his ankle issue has been a big reason he's struggled in recent times and think maybe his solid 2nd half last year means his ankle was finally feeling good or he had more confidence in what he could do without worrying about a setback.
I'll go have to listen to tonight's Dodgertalk and see if Skip thinks Kemp was traded because his value is higher now or maybe the Dodgers know his ankle might be a problem for the rest of his career and will have problems staying in the lineup.