There is always a situation under which any starting quarterback may get benched.
No quarterback understands this better than TB12 who works every game as if he's trying to keep his job.
While this is true, it would take a LOT for the elite QB's to get benched. Happened to brady 3 years ago against KC. Why? Because why risk him getting injured when the game was in the bag. Nothing he could do would change the outcome. Give the back up an opportunity to play. He didn't get benched because BB was considering replacing him with JG.
You would need to see a pattern of continue failure week after week before a QB like Brady would not start a game. And the same goes for Rodgers, Russell, Ryan, etc.