I see lots of people try to use Aaron Rodgers as an example to sit Blaine Gabbert, and it's one of the most disingenuous things I've ever seen written/said. Just stop, please. They're not in the same situation. When the Packers drafted Aaron Rodgers, he fell into their lap. They didn't move up to get him. They also had some guy named Brett Favre quarterbacking their team.
Every time someone says "Gabbert should sit, just look at Aaron Rodgers," it kills me inside, because they're situations are completely different. Everyone seems to forget also, Aaron Rodgers sat for THREE full seasons before he started. He sat not because he wasn't "ready", he sat because Brett Favre was still better.
If David Garrard can't beat out Blaine Gabbert in training camp, he won't start. They're not going to just sit Blaine Gabbert for the sake of sitting him. Brett Favre continuously beat out Aaron Rodgers. Once the team felt the were close, they moved on. They traded Brett Favre away and started Aaron Rodgers. Would Rodgers have been just as good if he had started right away? I have no idea. There's no way to tell.
If Gabbert's close to or beats out Garrard, he'll start and Garrard will be gone. If he's not, he won't and Garrard will start until the coaching staff deems it's time to make the switch. It's rather simple.
Saying "Look at Aaron Rodgers," is akin to saying "Tom Brady" when looking at finding late-round franchise quarterbacks. One example doesn't make proof, one way or another.