Manning does have a bit of pressure on him because he puts it on himself. He does have a lot to prove this season as well, but I wouldn't say he has the most to prove.
This isn't about what he's done in his career. His career is already HOF worthy and speaks for itself. We already know that. But this season he has a lot of questions to answer. And I don't buy the "if he doesn't do well then everyone can just blame his neck" excuse. That's bullshit.
His neck can only be used as an excuse if he suffers an injury. If he just plays like shit I'm not going to give him the neck injury excuse. That's a cop out.
He is still widely considered one of the best quarterbacks in the game and is expected to play like one. Not only that, but he's expected to win the AFC West and take the Broncos to the playoffs.
Will this season destroy his legacy? Of course not. But for this season and this season only, he is facing more expectations and has more questions surrounding him than any other in his career. And if he succeeds and wins a Super Bowl ring, he will firmly cement himself as the greatest quarterback of all time hands down, in my opinion.
A lot of people have picked the Broncos to win the AFC West and reach the AFC Championship game. In his first year with the team and after sitting out an entire year, how is that not pressure?
Pressure is felt when you have to prove people right or wrong. He has to prove to people that he is indeed healthy, that he was worth the money, that Elway and the Broncos made the right move, that he can still play at an elite level, that he can win a 2nd super bowl before his career is over or he'll retire with less rings than his baby brother.
He is already a hall of famer, but don't think for one second than Peyton Manning doesn't expect the very best out of himself and anything less than a Super Bowl is satisfactory. I don't care who you are, anybody in his position with that type of attitude feels a lot of pressure because he expects to be the best from the moment he steps on the field.
With all that said, there are plenty of other quarterbacks whose jobs are more in jeopardy but nobody expects them to do anything spectacular anyway so nobody will be surprised when they don't.
Different forms of pressure, I guess, but all these guys feel it to an extent. It's impossible to measure, really, but makes for good conversation.