I was recently training a young quarterback and he asked me “How do I know which drop to use”. I went into an explanation of how each drop correlates with a route and the drop is determined by the primary route in the concept or 1st progression.
I decided to take this a step further and describe the deep corner route. First, the route breaks at 18 yards which means it needs time to develop. The receiver stems his route in 5 yards and then pushes vertically for the remainder until he breaks at 18. How he breaks is determined by the corner and safety leverage. If you want more information and a video tutorial check out the youtube video I made.