I did watch the game for the 2nd time (as if the first wasn't enough) and it was an abyssmal throw. Then he misses Galloway on the TD fade that was knocked down by Henry. He may not have been able to fully step into the ball but he simply lacks the arm strength for these throws. It makes it hard on him and defenses know this so its even more difficult to move the ball. Factor that in and you have 8-9 man fronts on Caddy and we still cannot throw the ball with any effectiveness.
The pass to the endzone was released a fraction of a second late, and the defender only just tipped the ball. Rookies struggle making quick reads, it is part of the learning process. Grads might not be the answer but it is far too early to give up on him.
Arm strength actually has zero to do with "strength", its technique so they can work on that a little. Will he ever have a good deep ball, no that is highly unlikely, but he has sufficient range to play the WCO well and hit the occasional deeper ball.