This article came out of an interesting coverage tweak I noticed as I complete an off-season project to familiarize myself with the Gregg Williams' defense. I am charting every defensive snap the Rams' 2016 season, with the goal of using the results to write a variety of off-season articles about personnel usage, potential draft targets, fronts, coverages, concepts, and techniques.
This particular concept showed up on the tape several times. While it didn't create any turnovers, it did confuse Blaine Gabbert several times, causing him to pull the ball down and scramble.
The down/distance is 3rd a 10 - a perfect down for trap coverage is the ball is probably going in the air - and the offense is pinned fairly deep in their own territory.
The idea here is to show man coverage pre-snap in order to encourage a throw to the #2 or #3 receivers to the trips side of the field, where the trap CB will wait in the weeds to make a play on the ball.
In order to muddy Gabbert's pre-snap reads, the offense sugars the A-gaps with both linebackers pre-snap to create the threat of a blitz (would have to be a 5-man pressure with two deep safeties), follows the #2 receivers motion (used to flush out man or zone coverage), and aligns the strongside Nickel/CB at a standard off-man depth.
Again the idea is to show man coverage, encourage the QB to target the out-breaking route, and jump the throw with the squat CB.
Notice the left CB zone-turn (back to the sidelines to keep the eyes inside) at the snap to get eyes on the #2 and #3 receivers. He is not focused on getting a good jam on the #1 WR here as he would in a typical 2-deep, zone-under coverage because the deep safety to his side of the field is responsible for all of #1 vertical. The linebackers both back out of the blitz to play a pseudo-man technique known as 'Cut'.
This screenshot is straight from Nick Saban's 2015 playbook. The concept is fairly simple. Each defender will play all in-breaking routes (think dig, shallow, etc.) and vertical routes (post, seam, etc.), leaving any outside breaking routes for the CB. Notice how the inside leverage encourages a throw to the out route by the #2 receiver.
Gabbert clearly wants to target the concept to the trips side of the field, but he is forced to pull the ball down and scramble fairly quickly. My guess is he wanted the out route, but got confused when the CB appeared in his vision.
Gilbert's pick 6 against Indy came off the same trap/cut concept with a slot blitz.