49ers film room: Top 10 plays from Week 5 vs. Colts

Ray-Ray Armstrong interception (No. 1)

The Colts begin their next play on the 49ers’ 8-yard line, with 11 personnel in a shotgun bunch formation. The Niners counter with nickel personnel in a Cover 3 Sky variation, with the underneath defenders dropping back to the front of the end zone, and defensive tackle Earl Mitchell dropping back into short coverage.

Defensive coordinator Robert Saleh calls the perfect defensive play for the Colts’ pass attempt. Indianapolis has both outside receivers run out routes, while both inside receivers initially fake outs before converting their routes to posts.

Against traditional Cover 3 Sky, this route combination would likely put the free safety in conflict. With both corners on the outside receivers, and the inside linebackers responsible for the running back out of the backfield, unless the curl-flat defenders quickly recognize the post routes, free safety Jimmie Ward would be forced to choose between the two inside receivers.

Jacoby Brissett initially looks left to move Jimmie Ward away from the right side of the field. When he looks back to the right and sees that Jaquiski Tartt has remained in the flat, Brissett fires the ball toward tight end Darrell Daniels.

Unfortunately for Brissett, he doesn’t see Earl Mitchell has dropped back into coverage, which allowed linebacker Ray-Ray Armstrong to sink back into the end zone directly behind Mitchell. Armstrong is in perfect position to make a play on the pass, which he intercepts and returns 29 yards.

If Saleh knew the exact play the Colts would run, this is the defense he would use to counter it. The play’s 51-percent swing in win probability was the largest of the day:

Win probability: -51% (74% to 23%)