If Tatar sulks or plays poorly, then by all means trade him. I'd rather have a vet who wants to be here than some kid who's going to spend the whole season crying. At this point his attitude needs to be "I deserve to be on the team and in the lineup every night, I'm going to prove it," not "if I don't get my way I'll go to Russia," and he certainly shouldn't be saying that publicly. Those comments make me wonder about his intelligence too, since he should know that a) he probably wouldn't clear waivers and would end up in the NHL on another team, and b) even i he did clear waivers he can't just go play in Russia unless Detroit lets him.
If any kid is going to get sent down, it will be Nyquist. He's the only forward who doesn't need to clear waivers, and they will NOT go into the season with 6 d-men. If that happens, it's either going to be for a week or two max, or the whole season, and they would still have to clear about $1.5 mil in cap space after that. That means trading a vet, or waiving Eaves and trading Tatar. If they trade a vet, Emmerton can go as soon as Helm is ok.
This is how I see the roster shaking out after it's all said and done:
Andersson centering 2 of Cleary, Miller, Bertuzzi, Samuelsson, or Tootoo, one of those last 3 will be gone, the other of the guys not in the lineup as healthy scratches, with Tatar rotating in and out as well.
Eaves and Emmerton waived
I think Tootoo is the easiest one to trade, so he's probably the one most likely to be gone.