The 3-site defense and how it hinges on reading the No. 2 receiver’s release – The AthleticJune 1, 2022
In the NFL, when offenses want to get a chunk play against Cover 3 zone, one of the favorite ways of doing so is to get a receiving tight end or a wide receiver matched up on a linebacker by lining up in a three-by-one formation and running a deep crosser.
In this diagram from Alabama’s playbook, the defense was in “3 (buzz) mable,” which is a variation of Cover 3 in which the cornerback to the weak side (the side with one receiver) plays man coverage, while the rest of the defense plays its usual Cover 3 responsibilities. In the diagram to the left, the tight end runs a crosser and the mike linebacker (M) has to cover it. The mike has natural inside leverage on the route, but in the NFL that could be a serious mismatch if you have a linebacker who doesn’t run well and the tight end is someone like Travis Kelce.
To counter this, in passing situations, defenses will play “3 (buzz) weak,” which will tell the safety on the weak side to play the mike’s responsibility. That underneath zone is called the “hook” zone.
In this diagram from the Seahawks’ 2013 playbook, the free safety is lined up on the weak side and plays the weak hook zone, while the linebacker (S) lines up outside and plays “buzz,” which is an underneath zone to the perimeter. On first and second down, when the run is more of a threat, putting a safety who isn’t used to playing inside runs can make the defense susceptible against the runs.
One of the ways that Vic Fangio and his disciples will play Cover 3 while getting the best of both worlds is by playing a coverage that some coaches call 3-site. In 3-site, the weakside safety and linebacker read the release of the No. 2 (second-farthest inside eligible receiver) before deciding where they will drop.
Here, the Broncos defense had 3-site called. The Chargers had a three-receiver bunch to the offensive left (bottom of the screen), so that was to the strong side. To the weak side, the running back was the No. 2 receiver, so the weakside free safety and linebacker were reading him.
The running back released vertically, so the safety played the weak hook while the linebacker buzzed to the flats.
The coverage worked as it was designed: The safety matched up on the receiver running the deep crosser, and the linebacker covered the shallow route underneath, which is easier to cover.
On 3-site, the weakside safety and linebacker will switch assignments (safety in the flats and linebacker in the hook) only if the No. 2 receiver free-releases to the flats. One of the reasons behind this is that offenses don’t usually free-release their running back outside if they’re running four verticals.
In this diagram of four verticals from the Saints’ 2015 playbook, the running back has a check release, meaning he has to check if there’s a blitz before he releases outside. This is the standard way of running four verticals.
If a defense played 3-site against this, the safety and linebacker would see the running back check release, and the safety would end up in the hook zone to cover the crosser from the tight end.
As with any other coverage, an offensive play designer can take advantage of it by understanding the rules of the coverage.
Week 6, 0:51 remaining in the second quarter, second-and-19
Here, the Ravens lined up receiver James Proche at No. 3 and ran a crosser. The Chargers defense was in 3-site, so the weakside safety and linebacker were reading the release of the running back.
The running back free-released outside, so the safety covered him and the linebacker had to cover Proche on the crosser.
Linebacker Nick Niemann couldn’t run with Proche and left him wide open. Of course, the Ravens can free-release the running back on a concept that takes some time to develop because they have Lamar Jackson, who can get away from pressure.
The 3-site defense is also advantageous against play action or run-pass options because it takes away some of the run-pass conflicts that the weakside linebacker has. He doesn’t have to worry about having to sprint back to play the play action in case of a run because the safety would play the hook in that situation. Also, many quarterbacks read the weakside safety to decipher the coverage, and when the safety pauses to read the release of the No. 2 receiver it can cause some hesitation because he doesn’t declare his assignment like he would in other coverages.