Stanley was a NFL draft pick, tough to beat those guys out. Heck even a 3rd rd. pick like CJ took a few years to overtake a 5th round pick Ruddock. Petras will be just fine.
What does the NFL have to do with how good you are as a college player? Stanley was an average at best CFB QB. His career QB rating is 131, he was completely immobile and he never completed 60% of his passes in a single season. Even Lanning could get a 130 career QB rating but he could at least run