Juan Diaz is incredibly overrated on this forum. Are people forgetting that he got battered by a FADED Nate Campbell? Johnston beat by far the better fighters, as Diaz's best win was over a Corrales' leftovers version of Fritetas.
Ok, all of that may well be fair and true but this is h2h and in my view, Johnston was the better technician and I think he'd be too slick defensively for Diaz who was a bit one dimensional. It's all opinions at the end of the day though...
You lost all your credibility when you said that Lazcano fought Castillo on even terms. Castillo won that fight 9-3. At WORST, 8-4. Campbell exposed Diaz for the front runner that he was. And Frietas was past it when Juan beat him. He was essentially done after Corrales stopped him.