I appreciate this conversation and I think this issue is a really difficult one. A few things to point out:
* As bad as it has felt, Rooker has a .691 OPS. Now, you might scoff at that but I think we forget that we're in a pitcher dominated year (in part because they are a bunch of cheats) but that OPS is not terribly far from the norm. I'm not making a value judgement on that, merely pointing out that it's fair to point out that he shouldn't be compared to historical examples of what would impress us. He should be compared to his peers now. By that comparison, he hasn't been "bad". Not "good" either, but not bad.
* The team drafted way too many guys who can't field. That's the real issue here.
If I'm the Twins I give Arraez a 3B glove and give him extensive work there all offseason. That's his new home. Donaldson looks washed, certainly like he's going to struggle to deliver on that price tag. Trade him and move on. That means with Sano getting some reps at 3B as well you have some room at DH to play a guy sometimes. That means Rooker may have some options to play at 1B, DH, or LF from time to time with enough consistency to evaluate him. I think Marten is the future LFer and could be a really good one defensively and offensively but he will need most of next year. The problem for Rooker is he has to fight off Larnach, Sano, Marten, Gordon, Celestino, etc.
But as long as he has an option, with his draft pedigree and flashes of potential, I don't make that decision now. I keep him on the 40, I work with him on his defense and improving his approach, and hope he can hold down regular at-bats next year to see if we can find out if he has value or not. We have time, we should take it.