First, I see no way Kellen Moore enters into this equation in any way, shape, or form. KM is a non issue.
Second, the only person I see being put on notice here is Grier, not #4! Lance being dumped for practically nothing after the price that was originally paid to get him, I don't think he can even put Rush on notice. Not till he has adequately proven his value, and that's not going to happen overnight.
Third, The best of all 3??? Rush? I'm not a big fan of Dak, but neither do I hate the guy beyond all sense of reality. Rush is NOT the best of all 3. He's far and away better than Grier, and he's a good backup, but he's not better than Dak. It's not even close.