This will bring the defender to the ground, thus giving the QB a better view. On other plays, such as a screen, the line will fake very poor pass protection. The purposely allow the defenders to penetrate very deep. When the ball is flipped out to the back, these players will be to far upfield to chase down the ball carrier. Many of the short yardage routes include 5 yard in routes and out routes, along with the slant pattern and the curl route, where the receiver comes back to the quarterback.
Some plays incorporate a deep route to help open up the short passing lane.
The timing between the receiver and quarterback is crucial. The receiver should expect to see ball and adjust to make a catch as soon as they reach the first break in their pattern. Backs utilize swing patterns and routes into the flats. Passes to the running backs are very high percentage and often used as an outlet if all receivers are covered. Because short yardage pass plays happen so fast, the backs that receive the ball usually have an opportunity to break tackles and move the ball upfield.