To answer your question it would most likely be the decision making. Mechanically, the things he needs to work on a fixable. Footwork is the part that will help him throw passes with more authority more consistently but his release is great. Decision making is my concern to answer your question but I'm not really worried about it to be honest. Teams are game planing against him to the fact that he is a rookie and has never seen this stuff before. Most of these teams are playing things they normally would play against other qbs but they are intentionally trying to confuse him. 

 

To me, the biggest concern is if the fans are willing to give him a chance to  develop. He really stepped into a bad situation here. We are so desperate for a winner here and I think we tend to forget we need other pieces to make that happen. 

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