A lot is based on a few high profile cases that seemingly validate whichever theory you back (good or bad). Not sure any serious study into the topic exists. I do think there are a few main theories that try to at least ascend simply anecdote; 1. Their confidence ruined. "This guy is gonna be so overwhelmed in the moment. You need to put him in a place to succeed or his confidence will be crushed" I personally find this explanation crap. If he can't handle adversity, he isn't a franchise QB 2. You'll get him killed This is basically the David Carr defense and also used anytime it isn't an all pro line established. I generally find this to be bunk too, though there could be an extreme case where it was applicable, I suppose. 3. He needs to learn an NFL offense/reads and/or mechanics. This is similar to 1 in the sense that you're worried the guy will be overwhelmed by the moment, but rather than his mind, you're worried about his skillset. Learning on the fly, a guy may develop bad habits, relying on whatever his particular skill set is, whether than his cannon for an arm or his legs/escapability, etc. rather than developing solid NFL QB skills that will consistently allow him to pick apart NFL defenses. I find this the most convincing argument in general terms. However, whereas it's probably a concern for say, Watson right now who needs to develop a lot of skills, I am not concerned with this line of thinking on Trubisky from what I've seen- his skill set is already pretty advanced, I dont see the big potential for bad habits to form as he learns on the fly. It also probably helps that he doesn't have one overwhelming physical talent he is going to lean on too much. Plus, at the end of the day, the competition at QB is just too lackluster. After all, with most of the success stories on making a QB wait, they sat behind legitimately good talent. Agreed 100% with this. 1 is only an issue if the QB sucks at playing QB. People claim that guys like Aaron Rodgers, Steve Young, Steve McNair, Philip Rivers, etc. are good because they sat as rookies. And guys like Akili Smith, Tim Couch, Christian Ponder, Jamarcus Russell, etc. were bad because their teams were impatient with them and threw them on the field right away. When the common denominator is good QB vs. bad QB. Peyton & Eli Manning, Derek Carr, Roethlisberger all started pretty early on and were fine. Jake Locker, Brady Quinn, Brock Osweiler, etc. sat a year or more and it didn't help any. It's not about sitting vs. not sitting. It's about good QB vs. not good QB. 2 Don't buy that either. The OL isn't that bad. Hell, it's actually pretty decent. If he's getting hit too much, that's on the OC to adjust the game plan/blocking scheme to have extra protection in there. I think the Bears have allowed 4 sacks (not sure how many hits), but Trubisky would have been able to escape at least 2 of those by getting rid of the ball or getting out of the pocket. Doubt he'd be getting hit however much Glennon is either, since he's not a statue. 3 I don't know how you learn those things while not in a game situation. Can't get used to game speed by getting reps at 75% speed in practice. Cutler still had footwork issues when pressured. And like you said, there are plenty of reasons why this shouldn't apply as much to Trubisky as it does to others.