I would have to go with Britton, Stauffer, Lohse and then Santana.
I agree with one of the previous commenters in that Stauffer will provide a safer bet in Petco, but Britton has more raw talent (and potential) even though he is in the rough AL East. I personally like Lohse even though some people are skeptical; I think he will provide good numbers, maybe not great, but definitely serviceable. And Santana, I loved him but I'm just not liking what I'm seeing so far..CAN he turn it around, definitely...will he?? Thats the question, and so I don't know if its worth the pick up as of right now anyway. Hope this helps, goodluck!!