© Photo by Scott Winters/Icon Sportswire via Getty Images

With the unfortunate news of starting safety Juan Thornhill’s injury during Sunday’s 31-21 victory over the Los Angeles Chargers, the Kansas City Chiefs have to find a way to replace him immediately; before the Chargers game, Thornhill had played 96% of the team’s defensive snaps.

Last week I wrote about how cornerback Kendall Fuller’s role has been expanding into that of a safety/cornerback hybrid. Fuller could definitely play a part in how the Chiefs replace Thornhill.

But second-year safety Armani Watts could also play a significant role. After Thornhill left the game on Sunday, Fuller continued in his hybrid role — playing some at both cornerback and safety — while Watts had the lion’s share of the snaps as a true deep safety.

It’s worth noting that on Sunday, Daniel Sorensen still played the second-most snaps among Chiefs safeties — as usual, Tyrann Mathieu had the most — but played in the box for most of them. Still, he could get snaps as a deep safety in base personnel packages. Even if Sorensen is next in the pecking order, Fuller and Watts have to be ready to fill Thornhill’s shoes on the vast majority of defensive snaps.

So let’s take a look at Watts’ snaps from Sunday and see how he fits into the picture.

© Photo by Scott Winters/Icon Sportswire via Getty Images NFL: DEC 29 Chargers at Chiefs

The very first thing that jumps out as a difference between Thornhill and Watts is in what they are asked to do. With such a limited sample size, it’s difficult to identify hard trends. But even with a defensive coordinator like Steve Spagnuolo — who uses multiple coverage shells — this is a pretty obvious takeaway.

Once Thornhill left the game, the Chiefs didn’t mix in the single-high safety coverages — as they have done through much of the season. Instead, the Chiefs almost exclusively presented split safety or two-high safety looks.

Attacking downhill

Chiefs are going to have a difficult time replacing Juan Thornhill for the playoffs. Watts/Fuller should shoulder that role & I'd be surprised to not see a dip in creativity and increase in 2-high looks. Here Watts' IDs only route, sits on top, reads in-break, and closes quick pic.twitter.com/dCrIMUt4X5 — Matt Lane (@ChiefinCarolina) January 2, 2020

On this play, the Chiefs brought pressure — but the coverage behind it was quarters coverage, which tasks each player to cover a fourth of the field vertically.

Watts does a good job reading the routes and working down to the middle of the field as the receiver breaks to the inside. He shows good vision (and a quick click-and-close process) while coming downhill to make the tackle shortly after the catch.

Watts also does a good job identifying the tight end staying in to block — and when he sees the receiver’s inside break, he knows the offense doesn’t have time to attack his zone with a vertical route. So this is a good example of combining his own playbook knowledge with the situational football required on this play.

Even on this good play, however, Watts closes at a slower speed than Thornhill would. It’s not exactly a fair comparison — Thornhill is an elite athlete — but there is a noticeable build-up in acceleration before Watts can really close to the receiver.

Athleticism

Playing as a deep safety doesn’t necessarily require elite athleticism, but it certainly helps to have the fluidity to change directions — and the speed to cover a lot of ground. While there weren’t examples in this game where Watts displayed (or did not display) these abilities, it is still a cause for concern.

Tyrann Mathieu's ability to play in ANY role a team may ask from a DB is crazy impressive. A few weeks fighting 6'4" Courtland Sutton in the corner of the EZ and ripping the ball out of his hands he one-ups himself by sticking in 6'4" Mike Williams' hip & high pointing the INT. pic.twitter.com/UilJU6uiKi — Matt Lane (@ChiefinCarolina) January 3, 2020

Mathieu is amazing on this play — but let’s focus on Watts, who begins the play aligned as the deep safety.

Watts’ job is simply to bracket Keenan Allen — the outside receiver of the trips formation — which he does perfectly well. But watch how stiff he looks reacting to the double move — and his lack of acceleration out of the break; he should be trying to undercut the out route. Since Rashad Fenton has good position, there isn’t a real threat for a pass completion. But if Allen pushes Fenton vertically, it’s Watts’ responsibility to get under a comeback or out route. He simply doesn’t have the athleticism to do it.

We see this more often when he’s playing man coverage, but it’s something Watts displayed at Texas A&M, too. If a quarterback can influence him to flip his hips during a zone drop, he can struggle to recover if the play works back the other direction.

Ball skills

Another 2-high - Cloud this time - coverage w/ the slot to the trips working deep and Watts crossing the field to help over Ward - Watts tops a potential vertical - Stiff through his transitions but has best position - Waits for the ball rather than attacking it pic.twitter.com/YGAfugbH2g — Matt Lane (@ChiefinCarolina) January 2, 2020

This is an ugly snap for Watts — even though he is in a great position to make a play.

He stays on top of the vertical threat — and when it’s made, begins to break on the underneath cut. But then he simply misjudges the trajectory of the football; you see him stumble as he tries to read where it’s going.

This is his football. He’s coming downhill. Other defenders are in the vicinity. He has eyes on every player involved — and the ball — but instead chooses to sit back and let it fall into his lap.

Watts is a playmaker who has great hands — and the ability to make these kinds of game-changing plays. But as such an aggressive player, you’d like to see him challenge that ball in the air. In the postseason, a play like this could provide a huge swing; you’d rather see him attacking the ball.

Tackling

Chargers design the split zone well and get a hat on everyone in the box sans the FS. Watts has to read the play and run the alley to make a stop - Doesn't watch the motion, tracks the ball - Sinks down mirroring RB - Slides into gap - Comes in high and laterally pic.twitter.com/WdGoojXjzw — Matt Lane (@ChiefinCarolina) January 2, 2020

Another issue for Watts in his college days was his inability to finish tackles — both in the box and in the open field.

On this play, Watts doesn’t take the bait on the jet motion and does a good job mirroring the running back. That’s good. The Chargers are running a well-designed split zone and they execute it well, connecting on every block. That keeps Chiefs defenders up front from making a play — but also leaves Watts completely unblocked.

When the running back presses the A gap, Watts gets sucked up a little too far — which forces him to work laterally into the running lane. At his size, Watts doesn’t have the power to slow down a powerful running back without momentum behind him. So because of his lateral angle — and his high pad level — he can’t keep the back from the end zone.

It’s hard to fault a free safety being unable to take on a high-end running back one-on-one — but at the same time, this is where a player can separate himself from others.

Aggression

In terms of the risks he takes and the angles he pursues, Watts is an aggressive player. That results in some big plays — and some big blunders, too. Watts plays aggressively on these two outside runs by the Chargers — but with entirely different results.

Watts near the LoS as a man defender on a TE on this pitch play - Reads TE's pull and quickly works laterally - Keeps eyes on RB - RB's hips tilt upfield, Watts slips under the block - Goes low to prevent as little yards after contact pic.twitter.com/PRIDtdSiQ9 — Matt Lane (@ChiefinCarolina) January 2, 2020

Here, Watts gets outside of the quick pull from the tight end to hold his contain responsibility — and is able to get his eyes back on the running back. As the back tilts his hips upfield — indicating a vertical cut — Watts is able to slip underneath the tight end’s block on the inside and make the tackle.

Watts read the play nearly perfectly — and his aggressive decision to cut inside the block saved a good chunk of yardage.

Watts working as the near deep half defender on this outside run - IDs pitch quickly - Works downhill to fill - Takes overly aggressive angle - Never sees pulling blocker/tries to slip under - Gets pinned inside and blocks 2nd level pursuit pic.twitter.com/YAvrsf2RKv — Matt Lane (@ChiefinCarolina) January 2, 2020

This time — working as a deep safety — Watts comes downhill as he sees the pitch coming and again takes a super-aggressive angle.

Rather than working over the top of the running back — coming down at a 45-degree angle — Watts attacks more vertically. Then tries to turn and run with the pitch along the line of scrimmage. He missed the pulling blocker — and simply didn’t have the athleticism to redirect and keep up with the running back.

Even more troubling is that he gives up the ability to hold contain — which could have forced the runner back inside to the second-level defenders — while cutting off their pursuit by giving them extra traffic to work through.

Against both the pass and the run, Watts can make plays through his aggressive decisions. But he doesn’t always have the athletic profile to cash the checks he’s writing with those decisions.

The bottom line

In Thornhill’s place, Watts had an up-and-down game against the Chargers.

We saw aspects of his play on which he can build: his ability to process the field, his understanding of the playbook and game situations — and his willingness to attack the running game at the line of scrimmage. On the other hand, we saw some warning signs: a lack of athleticism, some over-aggressive tendencies and limited versatility in man coverage.

So who is a better replacement for Thornhill — Armani Watts or Kendall Fuller?

Fuller offers a bit more versatility. He is able to drop into the slot for man coverage, shows far more fluidity in his hips and may maintain a better last line of defense mentality.

On the other hand, Watts has played safety longer. He seems to have a good understanding of the playbook and how to process the field from his position. He also has a playmaking style similar to Thornhill’s.

With the extra time to prepare for the next game, I’d lean towards Fuller taking more safety reps. He has more potential to play as a single-high safety — and with his man coverage ability, offers additional versatility.

But if the cards fall his way and the Chiefs need him again, Watts will certainly be ready to show his progress.