My question is why did they bring him in at all if they intend to cut him? By playing to his tendencies, he is burning reps that could have been given to other players and better work other offensive components. Tebow may have hit on 65%+ of his college passes, but he is 50%- on pro passes. The Pats have been a team heavily reliant on short to intermediate routes that require laser precision. Inaccurate passing in those areas typically leads to interceptions. Unless Tebow fundamentally changed his play, which would seem highly unlikely if not impossible, he does not fit the Pats offense as a QB, so preseason simply proves what game film already shows - he can run, but he cannot throw an accurate pass. The Pats did not need to add him to the roster to prove that proposition.
Tebow is very athletic, and could probably be a viable player in a number of other positions. While his preseason work is sufficiently bad to merit something worse than simply being cut from the team, I believe he may stay with the Pats for some other purpose, whether fullback, tight end, or otherwise. No way do I see him joining the Pats as a charity project or to see if he can one day become a legitimate QB rather than a gimmick.
