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Chiefs-Broncos film review: a defensive back statement game, Juan Thornhill question answered

The defensive backs had a better outing than we have seen in a while against the Broncos, and in the process, we learned why the second-year safety’s snaps have been cut back.

NFL: Denver Broncos at Kansas City Chiefs Jay Biggerstaff-USA TODAY Sports

Any Kansas City Chiefs fan who listened to press conferences last week knew the defense was fed up — but fed up with what, exactly?

That was the question that needed to be answered.

Steve Spagnuolo’s unit hadn’t been playing its best football of the year — but more than not playing great, there was a general feeling that they were being beaten down physically. It was prominent among fans and even national media members that the defense seemed to be on the ropes, and the players felt that energy.

No player made that clearer than Tyrann Mathieu in the way he carried himself leading up to the game against the Denver Broncos. Mathieu is looked to as the leader of the Chiefs defense both on the field and off. His mindset sets the tone for the rest of the defense, and no one commands the attention or effort that he does when addressing the team.

Given how public Mathieu was with his frustration, this was a big game. He was fed up — and the defense was fed up. It was time to figure out how it would respond.

The defensive backs — and safety group in particular — came to play against the Broncos, and as a bonus, answered a question we have had for the past month: “Why isn’t Juan Thornhill playing more?”

The Chiefs’ defensive backs

The good

As a surprise to no one, the good this week came from Mathieu, who had a monster game.

Mathieu made his presence felt on the very first series of the game, as he hauled in a rather easy interception on an underthrown pass from Drew Lock. It wasn’t exactly a high-level play, but his man coverage skills are evident. Mathieu quickly breaks to take away the Out route, and as the tight end tries to turn upfield along the sideline, Mathieu just sinks right into his hip.

The football should never have been thrown, and Mathieu does a good job going and taking it away when the opportunity presented itself.

With L’Jarius Sneed taking over many of the nickel and even some dime slot defensive back snaps, it allows Mathieu to “hunt” and roam the middle of the field even more.

With the linebackers in a dog technique (blitzing as eligible receivers stay in to block) Mathieu is looking to cut anything over the middle of the field. He sees the wide receiver working a drag across the field and does a good job stepping down and mirroring the route until the receiver clears traffic. Mathieu then avoids the bodies and drives on it, taking away the potential pass.

This was not overly flashy, but moving Mathieu out of the slot and allowing him to play in a robber role more often will give him a chance to make quick reads such as this play or later in his game-sealing interception.

Safety Daniel Sorensen is always active in the run game, but in this game in particular, many of the defensive backs were getting involved. Working inside the box, Mathieu is able to stack the tight end, extend the outside arm and shed inside and get to the running back. Working over the top, Sneed is also filling in aggressively as he flows with the run.

The solid

Daniel Sorensen makes our solid section for simply being himself: a steady, constant presence.

Sorensen is at his best coming downhill — usually to the flats — after aligning deep. He reads the field cleaner and takes more accurate angles from these positions, and as we all know, he has no problem delivering a big hit. He does a good job working over the top of this Out route, making sure it wasn’t turning upfield, and then closing fast. It is good form on the tackle, as he gets his helmet across the hips and hits the bigger player low, taking him down before the first-down marker.

Sorensen had another play coming from a deep safety spot on a Swing route that was a Frank Clark deflection away from being a pick-six. Sorensen catches a lot of heat for garnering extra playing time and being played deep, but he’s consistent and it’s arguably his best position.

Sorensen knows the coverages, plays strong angles, and he simply operates better in space and coming downhill than he does in the box or in the slot.

Focusing on the second play in the clip above, Sorensen again shows why he continues to see the field. That’s a strong play against the run — coming from deep and closing the alley against a running back who is still working through his reads.

Sorensen isn’t without his flaws — he was beaten on a couple of Out routes and can be easily sealed when he plays as a dime linebacker — but there is a certain level of consistency in his play on the back end. Pairing that with aggressive downhill plays, he’s easily earned his reps.

The bad

Unfortunately, Juan Thornhill continues to make this category in 2020, and it’s ultimately led to less snaps throughout the year.

The aforementioned Sorensen is caught on the back side, but this play really falls apart front side. With Ben Niemann taken care of, a very clear alley opens, as Denver had a numbers advantage and good angles. That alley has to be filled by either Mathieu, who has to replace contain, or Thornhill, who simply never addresses the run. By the time Thornhill reacts to the run, the running back is five yards beyond the line of scrimmage heading into the open field. Then Thornhill takes a rather poor angle as if he didn’t get eyes on the running back and allows an even bigger gain.

Plays like this litter his film in 2020. His lack of consistency filling interior runs when playing deep and the poor angles to the ball have forced the Chiefs to use him more sparingly. You add in a lack of ball production due to opportunity and play, and there isn’t much of a reason to see Thornhill continuing to get big snap shares.

The emergence of Sneed does not help Thornhill’s cause.

L’Jarius Sneed’s impact on the safety rotation

Sneed played a fantastic game against the Broncos — both in coverage and against the run.

I’ve mentioned it a few times, but the Chiefs are using Mathieu as a little bit more of a chess piece, and it’s made possible because Sneed has been very good as a slot defensive back.

Sneed plays great coverage from the slot in a Cover 0 look, knowing he can’t give up anything short and redirects the wide receiver. Sneed easily turns to run with him and almost capitalizes on the throw.

Sneed may have been the most physical run defender for the Chiefs against the Broncos — even garnering some reps as an actual box player, which helps make the transition easy.

But what does this have to do with the safety rotation?

With Sneed taking over the slot reps, that also means he’s taken over the nickel reps. In the nickel defense, Sneed played 100% of the snaps while Thornhill saw zero.

The Chiefs have transitioned from a Buffalo sub-package — three safeties and two cornerbacks — to a traditional Nickel. The Chiefs are opting to alternate Mathieu and Sorensen as the deep safety or both in split-field looks. As mentioned, Sorensen is just simply consistent when playing deep coverage and knows how to read the field but still can come downhill to make some plays.

Having the versatility to move Mathieu around makes playing Sneed in the slot, who is also playing better, more valuable than forcing Thornhill into a deep role. Given his struggles in terms of tackling, fitting the run and taking quality angles, that takes Thornhill out of the base package personnel grouping as well.

The bottom line

After a rather public and animated couple of weeks, the Chiefs defensive back room had a huge game against the Broncos. Mathieu played arguably his best game of the year in every aspect, including interceptions at both the beginning and end of the game.

Sorensen continues to show why he belongs on the field for consistent play. Sneed’s excellent play continued, and he has shown he can excel in the slot and outside. The odd man out is Thornhill, who has left fans desperately asking for safety rotation answers, and we may have gotten them through the play on the field.

Thornhill still looks like a guy recovering, battling some issues stemmning from the injury. He just isn’t performing as well as other options in just about any role at this point. There are times in which giving Thornhill snaps almost feels as though the Chiefs are playing with fire, and the defensive staff simply can’t have the big plays happen.

Hopefully, as Thornhill regains his athleticism, he gets more confident in his reads and his angles of pursuit and can regain his role as the predominant deep safety, but until then, he has been relegated to a dime defensive back.