Just like putting Janis in the game and run him deep to hold a safety deep protecting against a deep route, just like running slants can setup a defense for slant and go's, running a screen or two makes defenses protect against it. And also to setup other plays. If they run Starks/Lacy into the flat and hit him on a screen, a LB has to follow him, which removes a defender from the middle which could make a bigger hole for Cobb crossing the middle, or pull defense out of position allowing for a TE to sneak out the other way.
Originally Posted by: PackFanWithTwins