So he had a bad practice. It's the 2nd one of training camp. And he picked it up towards the end of practice. Rex himself said EJ had a good practice yesterday. IMO, it's a bit early to worry. Actually what's the point in worrying, what are they going to do? There aren't very many options at QB, they are pretty much stuck with what they got for now.
Edit: and I'm in the 40/60 group on if EJ will succeed. It's still a long shot but they are stuck with who they got. Just got to hope the Roman can mood the offense to whoever wins.