Is he deliberately playing bad?
No i dont think so.
Is he watching enough film, training hard enough since dumping Nick Hicks' training company and putting in the hours nessesary to maximize his potential on Sundays?
No, and you'll never convince me otherwise.
His athletic ability has clearly declined, I dont know if its due to a degenerate hip or other injuries that have piled up or hes just not in football shape but hes never been slower when running and his arm has never appeared weaker.
But whats even more troubling than that, is his decision making/mental side of the game. If its not a screen pass, you can count on one hand how many "good" throws he makes per game. On deep passes, it seems like Tua just throws it as far as he can and starts praying as soon as the ball leaves his fingertips. If its not a 5-10 yard crossing route or screen pass, Tua either doesnt make the throw (and usually gets sacked) or chucks it downfiled. There isnt many plays in Tuas career where he goes through more than two progressions on any given play and his attitude after making a bad INT or missing on a 3rd down or going 3 and out, is always the same. He trots over to the sidelines with a smirk on his face and an "aw jolly, gee shucks ohh well" attitude after performing badly on the filed. I dont see the fire in his demeanor that leads me to think he cares very much about how his play is hurting the football team.
To make a long story a bit less long; Tua just isnt very good. Hes average to below average whos being paid top 6 QB money.