Cover 3

Bails at the snap and takes the deep outside third. His job is to not get beat deep. Plays with outside leverage on #1, funnels everything inside toward the FS. Gives up the underneath throw to protect the deep ball.

Mirror on the other side. In Cover 3, the CBs are essentially deep safeties — they give up the short/intermediate game completely. This is why quick outs and comebacks kill Cover 3.

Plays the deep middle third — centerfield. Aligns 15+ yards deep and reads the QB through the #2 receivers. Must get to any deep throw in the middle of the field. He's the last line of defense for everything between the hashes.

Rolls down to the LOS level and plays an underneath zone — usually the flat or curl-flat to the strong side. This is what makes Cover 3 a '4-under' scheme. He's essentially a linebacker in coverage. Also the primary force player vs the run.

Drops to the weak-side hook-curl zone. With only 4 underneath, his zone is wider than in Cover 2. Must be alert for crossing routes and dig routes coming from the strong side.

Hook zone in the middle of the field. Same as Cover 2 but with more ground to cover because there's one fewer underneath defender. Reads QB, walls crossers, and fills vs the run.

Strong-side curl or seam-flat zone. In some Cover 3 variations (Buzz), the SAM replaces the SS as the flat defender while the SS takes the deep third.