If what the article claims is true and Hayden is a definite to make the roster, then I think the other spots will come down to versatility. The article claims that one roster spot will go to the backup 1-tech role between T. McClain, Coleman and Bishop. It also claims one of the other spots will go to either J. Crawford, who has been playing primarily at 3-tech, or Gardner, who has been playing primarily at SDE. If that's the case, I think it rules out a guy like Bishop who seems to be a pure 1-tech. McClain and Coleman can play either DT spot, and J. Crawford and Gardner can play either 3-tech or SDE. I wouldn't be surprised if the last two spots go to a 1/3 DT and a SDE/3DT. I'd prefer to see Bishop battle Hayden for the one true 1-tech spot, but I don't know if I see that happening.
My prediction is Coleman beats out McClain because he seems to be more reliable from a health standpoint, and I'll give J. Crawford the nod over Gardner at the moment just because I've never seen anything from Gardner.