A screen pass is, in the general case, any play where the quarterback passes the ball to a receiver or running back who has one or more offensive linemen in a good position to block for him. Some types of screen plays include:
- Running back screen This is perhaps the most common screen pass, and it is a cornerstone of the West Coast offense. I'll explain this from the perspective of a standard I-formation, with the tight end on the right, running the play from the right hash mark. The quarterback drops back to pass, and the wide receivers and tight end run their pass routes as decoys. The halfback delays for a second as if he's blocking and then sneaks out into the left-side flat (the area behind the line of scrimmage to the left of where the offensive line started). The left guard and center block briefly and then detach themselves from the pocket protecting the quarterback to form the screen. The fullback is responsible for ensuring that at least one of the defenders coming through the area vacated by the screening linemen is delayed long enough for the quarterback to throw to the halfback. Now the halfback has the ball and two lead blockers, and most of the defense should have either pursued the quarterback or the other receivers.
- Quick wide receiver screen While this is not as common a play as the one above, it can be quite effective when run properly. The receiver will step back a yard or two into the backfield, and the offensive tackle on his side of the field will detach from the line and block upfield as soon as the pass is complete. It requires the defense to be playing in zone coverage, preferably a cover 3 rotating away from the play or a cover 4. In man-to-man coverage, the cornerback will follow the receiver on the screen and hit him as the ball arrives. In a cover 2 zone, the corner is responsible for the flat area and will still be responsible for reading the play. In a cover 3 or cover 4 scheme, the strong safety and free safety are joined in deep zones by one or both of the corners, and whoever is dropping back to a deep zone is less likely to read the screen quickly enough to stop the play.
Sources: lots of personal experience with Madden 99--2001
Bill Walsh, Finding the Winning Edge