(Pictured above is a diagram of this play)
The Eagles love to get the ball to Brian Westbrook in space, and they commonly do this by calling screen plays.
However, the screen was not called as often as it has been the past few seasons, due in large part to the aging of offensive tackles Tra Thomas and Jon Runyan.
Because of that, Reid had to be a bit creative in how he put Westbrook into space. One way he did this was by calling a "jerk" route.
The jerk route is sometimes called out of a split backfield, with two receivers and a single tight end. Basically, the x receiver can run several different routes, but usually he runs a post. The Z receiver also runs a crossing route.
The "B" running back runs towards the sideline, while the tight end(Y) runs a corner fade. This allows the running back(A) to get into the middle of the field, and usually he gets matched up one on one with a linebacker.
With Westbrook, this is a matchup nightmare for defenses.