I also think the biggest impact is on his teammates. They saw cowardice. Players will not put out for a coward.
We used to call it reckless abandon.
If we were standing up at the end of a play, we got yanked.
Newton was frustrated, just as Brady was. The difference between someone who had been there before and a first timer was evident. If you don’t will yourself to win, everyone knows it.
Not only did his teammates see him sag and melt under pressure in that game, his opponents did and fed off of it, and the rest of the NFL players who watched it as fans saw it.
He’s toast. My prediction is that he will be a serviceable quarterback, but he will never be great. He is going to get injured, and is always going to have excuses why he isn’t taking the next step. I wouldn’t be surprised to hear him eventually play the race card.