Written by Sam Monson (PFFSam on twitter) who is the same guy who put Brady in a coffin in June of last year. I have a hard time putting any stock into anything Monson says after that gaffe.
http://insider.espn.go.com/nfl/insider/story/_/id/11020311/tom-brady-no-longer-top-5-qb-nfl
Monson did backtrack a bit after being hit in nuclear fashion by at least 25K Pats fans on twitter who pointed out the problem with the Pats wasn't Brady but the horrible play of the offensive line those first 4 games. He wrote this after the KC debacle.
https://www.profootballfocus.com/blog/2014/10/01/analysis-notebook-week-4-3/
However, my own eyes have seen PManning's play deteriorate because of his physical infirmities over the last 2.5 years so, yes, I've seen he's been on the decline physically and don't need Monson to tell me that.
Now Monson says Manning's brain is also in decline & that Manning is misreading defenses. Monson points out a couple of plays as proof. It seems to me Monson shouldn't make that accusation without first asking Manning what he was seeing and thinking on the plays in question. Instead Monson assumes what Manning was thinking...no can do.
To me those ints by Manning can be explained by this line written by Monson:
"He’s definitely leaving plays out on the field because of the lack of arm velocity."
Expanding that a little, Manning is making throws his mind says he can still make. Manning's bad throws, to me anyway, are because
Manning's arm strength is progressively getting worse and he has to relearn his diminishing ability in every game he plays now. Iow, those bad passes are a result of Manning's progressive diminishing physical ability rather than his mental ability imo.