A lot of the time people say "a player is being moved at his lowest value" it's not actually true. The whole point of making a move now is because he has lost faith in Kemp, and wants to move him before people get an extended look at declining production (not saying I feel that way about Kemp, I'm just saying that's what my strategy would be if I felt poorly about him).
My point is, if you have a slumping player and you think it's a realistic snapshot of what he's going to be moving forward, you move him. You don't wait around for people to start feeling the same way as you.