Where? His ERA? Yeah, but ERA rarely tells the whole story. His BB/9 and his H/9 were nearly identical as was his 1.49WHIP. I dont know why you love this guy so much. Think about it objectively.
If he is a project, then what are they hoping to accomplish?
Is he a guy with lights out stuff an no command? No. Guys with lights out stuff typically dont give up nearly 10H/9IP and they would typically K more than 7/9IP in AA.
Is he a guy with good command and developing stuff? No, because he walked nearly 4 batters per 9IP in AA.
Is he a guy who would benefit from a change in role? Well, according to soxprospects.com, yeah. He is usually ok for the first 2 innings and then falls off the cliff. Okay, second question in that line of questioning, is he a guy who is a possible lefty closer or setup man? Not really. Most closers have lights out stuff, and he doesnt as evidenced by the first question we talked about above. Is he a lefty specialist? No at this point because he doesnt completely dominate them.
In short, Johnson is a guy with marginal stuff, poor command and limited endurance. If he wasnt left handed, I would say this guy has no shot at being a big league pitcher at all. That he is a lefty likely limits him to relief work in the future. Hardly a top prospect. I do agree that stats rarely tell the whole story, especially in the minors. But there are things you can look for in pitchers lines that tell you what kind of stuff they have. His numbers are average or bad all around