Abe Alvarez is a AAAA pitcher and will most likely never be a sucessfull starter in the pros.
Im not saying Foulke should start right away, but he isn't an effective reliever anymore and could possibly be used as a spot starter/long reliever. He needs to go on the DL and fix whatevers wrong with him, then my suggestion was is that he work on his other, lesser thrown pitches (slider, splitter) and maybe fill in as a 5th starter for a while or something.
If he has a couple rehab starts in AAA, and gets healthy again, he could seriously be a solid #5 starter. His WHIP isn't bad this year (1.22) and he has the ability to go 5, 6, or possibly 7 innings if needed. Just a suggestion, since he really has no other options left.