I truly have no idea who the Twins are going to call up to replace Hildenberger. There aren't many options out of the guys on the 40 man roster. Gonsalves, Mejia, and Vasquez are on the IL. Stewart, Thorpe, and Littell have been starting (and haven't been all that great). Addison Reed is on a rehab assignment, but has been extremely bad at AAA. Romero was just demoted, so I believe they have to wait to call him up again. That leaves Moya and his 9.53 ERA at AAA.
I guess there are a few guys at AA that could make the jump in Stashak, Bray, or Mason. Maybe they give Tyler Jay a shot even though he hasn't really earned it.