Anderson will be the best pitcher in that group at some point. Whether that happens when he returns or 2 years from now is the question. I think for the second half, JDLR is the best option, but that's just a hunch. I'd definitely rank Happ last out of the 4.
I'd go with Anderson here. He has the track record over Volquez...if he's healthy. Volquez to this point hasn't proven anything except that he can throw it 100mph. Maybe he's successful, but Anderson is the safer choice. And thanks for helping me out too.
Volquez. He is two years removed from an ERA in the low 3's and 200+ K's...He has hit 98, but has also shown pretty good control in his rehab starts (2 walks issued in one game was his most...). His team is hot and I like their bullpen.