An effective run defense requires two primary characteristics in order to be successful.

The first characteristic is inside lane integrity. The Colts utilize three interior defensive linemen in the base formation on early and rushing downs. Johnathan Hankins and Al Woods have the role of trying to “clog the middle” by requiring two offensive linemen to block. This leaves the other interior lineman, typically Henry Anderson or Margus Hunt either one-on-one or getting a chip from a tight end.

This is ideal because the more attention that is required by the interior linemen, the cleaner the inside linebackers can play behind them. They can see the play develop in the backfield and track the ball. They can fill inside rushing lanes if the back attempts to run inside the tackles. They can also move laterally to mirror when the play bounces to the outside. Antonio Morrison and Jon Bostic are particularly adept at stopping runs inside the tackles.

The second characteristic is edge containment. Edge containment traditionally falls on the defensive ends or outside linebackers. The way the Colts play defense, there is often a fourth down lineman playing in a “wide 9 position” that is lined up across from no one to the outside of the tackle. The way the team lines up can be important because edge responsibilities can shift depending on what the traditional end or outside linebacker is asked to do on a given down.

No matter who has the responsibility, at least one player is tasked with maintaining the edge. Ideally, this player will seal the edge and force running backs to the inside inside. Secondarily, this player will force rushers to run laterally behind the line of scrimmage. If the back can’t turn the corner, he will not pick up meaningful yardage.

When edge defenders fail to contain, the running back turns the corner with space in front of him. The back also typically has a size advantage against boundary defenders.

For much of the season, Indianapolis has done a terrific job with both of these responsibilities -- particularly early in games. However, on numerous occasions there is a sudden and surprising breakdown in the fourth quarter where opponents start to run the ball and chew clock at will. We’re going to try to figure out why.

In the first half, the Titans netted a total of 11 yards rushing the football. It was a dominant showing by the Indianapolis defense and part of the reason for it was plays like this one.

Notice that John Simon starts the play in a two point stance and identifies the run early on. He does not attempt to drive the tight end toward the middle of the field but gets a lockout and holds him in place to plug the outside running lane (contain). T.J. Green moves laterally to mirror play direction and Jon Bostic comes from the other side of the field to track the play down.

Even Pierre Desir stays to the outside of the play. If Demarco Murray tries to bounce the play outside, Desir is in great position to meet him.

I will also point out something that I noticed in breaking down film that I find frustrating in hindsight. While the play didn’t really go anywhere in this instance, Margus Hunt (#92) is pretty blatantly held by the guard when he tries to release from the block and get a hand on the runner. Keep an eye out for this moving forward.

Indianapolis is able to stop Demarco Murray for a big loss on this play and it all starts with Jabaal Sheard. He is able to penetrate into the backfield and cut off the outside running lane before Murray is able to get to the edge. Notice that Sheard’s primary goal is getting up the field and not to the interior. Also, Jon Bostic and T.J. Green both move laterally to help contain the play if it gets to the outside. Bostic even gives Green a bit of a nudge, suggesting that he get outside.

Remember the movement of players at the line and at the second level on this play when we take a look at plays in the fourth quarter.

This play is another example of discipline by Jabaal Sheard and Jon Bostic. It is also a display of dominance by Johnathan Hankins and Al Woods. The play was supposed to go to the left side of the field. Woods gets so far into the backfield that Murray has to redirect (notice the tight end hook Woods as he attempt to turn the corner and run down the play from the back side). While they are not important to the play, note that Hunt and Simon are also maintaining the edge to that side of the field.

On the backside, Hankins pushes into the backfield against a double-team. This forces Murray to run backwards to get outside of the tackles. Sheard and Bostic have kept their eyes in the backfield and stayed disciplined. While Sheard does not turn the run back inside, he does not allow Murray to turn the corner and the play goes for a minimal gain.

There was a second or two where Sheard could have easily made a poor decision to abandon the backside edge and chase play side. He doesn’t do this and the Colts defense stuffs the run.

Remember how Jabaal Sheard was patient on the outside early in the game? On this play he crashes inside and takes on the tight end at the line of scrimmage. He either doesn’t realize Derrick Henry is in the backfield or he expected someone behind him to have contain. Eric Decker down blocks T.J. Green who sucked inside prior to the snap. This leaves Henry one-on-one with Kenny Moore in space.

After such a strong showing throughout three and a half games, I tend to err on the side that Sheard slanted on this play by design. If true, this places more responsibility on T.J. Green, who shouldn’t have pursued up the field but should have mirrored Henry’s movement to the outside. His job is to kick the play back inside.

If Green was given this responsibility, the coaching staff is ridiculous. Asking T.J. Green and Kenny Moore to be primarily responsible for setting the edge against a running back with the size and speed of Derrick Henry is ludicrous.

I apologize for the long delay before the snap on this play but keep an eye on player motion and personnel here. After shutting down the Titans offense for the entire game, the defensive coaching staff decided to change things up.

Tarrell Basham is lined up with his hand in the dirt. He is pushed inside in a one-on-one battle with a tight end. Jon Bostic crashes to fill the gap created by Basham. When Derrick Henry does not have a rushing lane to the inside he is forced to bounce the play outside.

In this circumstance, T.J. Green and Kenny Moore are once again the boundary defenders who must contain the play from bouncing outside. As with the previous play, T.J. Green crashes toward the line of scrimmages and engages the inside shoulder of the tight end. This leaves Kenny Moore on an island 8 yards off of the line of scrimmage.

Once again, why sell out from a defensive front and defensive scheme that had been working all game in order to bring in Basham and Mingo? Sure, there is a chance you can get a sack if Mariota passes the ball but I’m not convinced that Basham and Mingo are more likely to create pressure than Simon and Sheard in the first place.

On this final play you see much of the same. Why does Sheard get so far into the backfield on a play where Henry is running up the middle? Notice that Simon plays to contain the edge on his side of the field.

Why does Bostic immediately move up to engage the left tackle? He is driven easily out of the play.

Why does Antonio Morrison crash toward the middle of the field instead of moving laterally to replace Bostic?

It is entirely possible that the Colts defenders who completely shut down the Titans ground game in the first half just forgot how to play football. It is possible they are not mentally resilient enough to maintain four quarters worth of discipline. It is also possible that they are being told to attack the line of scrimmage. It reeks of failed defensive adjustments and is consistent with what we’ve seen late in games in previous weeks.