We haven't seen enough of him to make a drastic opinion one way or the other regarding his adequacy as an NFL QB. From what I saw in preseason, he seemed to display accuracy and a decent arm. Those are the strengths we have seen till now. I hesitate to beat down on the guy for his pitiful performance in the Browns game.
As an aside, it is quite telling that Marrone is ready to start him over Flynn. Even though Flynn has not had enough time with the playbook, his experience should have propelled him to start over an UDFA rookie QB. But early this week, Tuel started taking more first team reps than him. Not a good sign.