The Chargers are in Nickel personnel on 3rd&10 vs. 11 personnel.
The Chiefs are in a 3x1 with the TE in a reduced split.
The pre-snap coverage look is 3 buzz weak playing a 4 under 3 deep zone coverage.Kansas City has a plan to attack the expected coverage on 3rd&10.
The route starts with the reduced split Y on a width release curl/stop route past the sticks. The route is designed to widen the Corner in his 1/3 as well as pull the curl-flat Will LB out wide.
The inside WR to the strong side is running a spot curl setting up on the opposite hash in the weak hook zone. The Slot is going over the top of the spot route on a deep over route. The goal is to create a high/low on the buzz safety in the weak hook. If the Safety jumps down on the spot route at the sticks the over route has a void to attack. If the buzz safety stays deep for the over the spot route can sit down at the sticks for a 1st down completion.
Strong side the RB swinging is designed to hold/widen the Hook/C-F defenders. The outside WR is running a basic. If the Hook dropper squeezes back inside with the crossing routes the basic can be a 3rd option after the high low on the weak hook.
The Chargers however are not running just a zone 3 buzz weak. They are flooding the coverage. The Chiefs have the RB strong representing a 4 strong load pattern distribution.
The coverage is man from the back side Corner. With the Corner handling the Y 1on1, the defense can distribute differently. With the Corner no longer playing a deep zone he no longer needs a C-F dropper to handle the routes in the underneath zone. The weak side curl-flat dropper can drop to the #4 instead of zone dropping the C-F. The defense now has an underneath dropper working to 1-2-3-4.When the RB (#4) runs a route strong the Will LB opens to the strong side looking for the first crosser. The Will is in great body position to handle the crosser coming back across on the spot route. When #4 goes strong the buzz Safety can pass the 1st crosser to the Will. The buzz Safety is free to handle the new #3 coming across (S) on the over route. By matching the buzz Safety on the over route, the void area the offense was attempting to attack is no longer available. Having the Will/Buzz Safety distributing this way eliminates the high/low in the weak hook zone. Strong side the Mike is able to get into the window of the new #2 (Z) on the basic while the C-F Nickel leverages the RB in the flat.
The Mike ends up squeezing inside with the QB's front shoulder intentions. With the spot and over routes covered the QB takes the Y on the 1on1 vs. the Corner in man. The QB is pressured by a great 4 man pass rush which helps force an errant throw. The pressure also prevents the QB from having time to work back to the basic route.
Cover 3 is a simple concept. Teams that run Cover 3 variants as the bulk of their coverage concepts have all the nuanced adjustments to handle whatever offenses throw at them.
Well done from the Chargers and Defensive Coordinator Gus Bradley.