I don't think he is going to make it in the NFL as a QB. Wide receiver, return man or DB would give him a better chance. QBs need to be intelligent, leadership and sound judgment. Marcus has none of them.
How do you know that he is not intelligent?
In any event, Brett Favre had a bad problem with alcohol in his youth as well. In fact, he says that if he had not gotten out of a big city like Atlanta and gone to a smaller, quieter community like Green Bay that he would have never righted himself.