I think they will happily go bullpen game, however you define that, for 2-3 weeks. It's unclear whether Covey is shut down or just kind of parked on the 60 at this point. But nobody wants that either.
God forbid, if Turnbull is seriously hurt, it just means Walker returns, so long as he can improve throwing that splitter at least somewhat. Somehow our expectation of what a 5th starter looks like (and also what a #8 or #9 hitter looks like) has gotten seriously inflated (which I suppose is also a credit to Turnbull, more than the team's overall success. And to Sanchez who no longer is one). A trade would just get you another Covey type.
Max Castillo?