You can't coach vision in a QB. You either got it or you don't. See Zac Taylor/Joe Ganz. TA is Martinez 2.0 minus the Forrest Gump straight line speed.
That's not entirely true. You can create an offense and a system that allows seeing the field and finding the open receiver more efficient, which I think could help his 'vision' on the field.
There were a lot of instances this last year where it's clear TA and his receivers were not on the same page. Our offense seemed to go through a kind of progression on some passing plays - a play is called in and everyone lines up, TA then checks the defense and communicates with the sideline to see if he needs to change something. He either keeps the play or audibles to something new. Then, in some instances, the receiver had a choice of which route to run depending on the defense, and it was up to TA (and the WR) to be on the same page to make a good throw.
That's a lot to think about, especially for a younger QB.
Now, I'm sure a lot of passing plays across the country involve option routes like this. But, either the coaching was bad or TA and his receivers just couldn't mentally handle it. Either way something needed to change and at times it didn't. Whether TA is or isn't the new quarterback, we need someone that can create an offense that will play to the QB's strengths, and Riley seems to be someone that's all about adapting what he does based on the players he has.
As a side note, as much as many of us like Joe Ganz, he's a glorified intern at this point in his career and yet he was coaching quarterback. The guy has a promising career but he was in no position to be doing something like that, at Nebraska, this early in his career.