The essence of a screen is letting the pressure head to the QB, while a lineman or two pulls for a block, and then throw the ball when half the defense is running the wrong way and your blockers are out front. We just throw the ball immediately at the RB. The defense hasn't had any time to get out of position and there's no time for blockers to get out front, so the defender is in the right spot and just tackles the RB for a loss or short hard earned gain.