It really doesn't. Rush lacks the physical skillset to be a starter in the NFL. Why can't we just be happy he was a competent backup? Why do we have to project something he's not capable of?
I am happy we have a competent backup....but if your backup wins 3 or 4 straight games, and looks going doing it after a long inconsistent stretch by your starter the conversation becomes very real. Now we still need to actually witness that Cooper Rush is capable of winning week after week in the NFL, which isn't easy to do. We are getting way ahead of ourselves with the talk of replacing Dak, but two or three more Ws makes that talk seem a little less crazy.
I agree completely that Rush doesn't have the skills to be an NFL starter in this league, and I'm skeptical the Cowboys can win the all of the next 2-3 games until Dak gets back, but this stuff happens more often than we think. It's how Dak got the job in the first place....even Romo was a backup until he was what 26 or 27 and got a chance? Carson Wentz was more physically gifted than Nick Foles. Kurt Waner was said to not have the physical traits to be an NFL qb. At the time even Bledsoe was probably a better overall QB than Brady. There are just so many examples of the Steve Youngs, Doug Flutie, Brett Favre stories where teams had given up on these guys only for them to turn around and go on either short runs of success or have hall of fame careers.
I'll still put my money on Dak being the QB of this team week 10, but everything sounds crazy until it isnt. It's why so many guys like Brady even want to give reps to their backups.