The worst thing for a defensive lineman to do when he sees a screen setup is freeze. In the video below, Winston DeLattiboudere (aka Coach DeBo), DLine Coach at the University of Minnesota shows how he teaches screen awareness, recognition, and retrace to rally to the ball carrier.
D-Line Screen Recognition & the Retrace is part 9 of the 10 part system: Coach DeBo's DL Keys to Victory. You can find all 10 sessions on Glazier Drive.
In the video, you will see both practice and game video to see the drills and the skills that he teaches.
You will face a lot of screens when you have a good defensive line.
You also have to be prepared for teams that throw a lot of screens regardless of who they face.
The worst thing for a defensive lineman to do is to freeze and look for an interception.
The best thing the lineman can do is help get numbers to the ball and get it on the ground by getting in the hip pocket of the offensive lineman.
Coach Debo likes to be the one simulating the offensive linemen so he can get a close-up look at their reactions.