I agree he might be injured, but two thought come to mind.
1) His play didn't start declining THIS year, He was similar last year. 2) Flame away if you want, but Belichick always says he does what is right for the team, but how is playing an injured QB helping the team or even right for the team ?
I said after the 2018 and 2019 drafts, Belichick isn't doing Brady any favors. TWO straight GREAT TE drafts, virtually ignored. 2019 draft, one of the greatest WR drafts in years, granted, they drafted one in the 1st round, but is he even the right one ? He seems to have ZERO explosiveness, and that's what this team needs. And why not double up on WR or even triple up. Your chances of one of them making an impact goes up if you have 2 or 3 of them. Mecole Hardman and DK Metcalf are exactly what this team needed, speed and explosiveness. Hardman adds exactly what the Pats needed, because he's a great return man as well.
Instead, you trade up for a slow DB in the 2nd round (AGAIN !) who hardly plays, when they had TWO 2nd round picks. Guess who went in the slots the Patriots had, Hardman and Metcalf.
So Belichick certainly isn't doing Brady any favors, but a good QB can succeed with crappy receivers, look at what Wentz has WR wise, so I don't want to hear any excuses.