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The Chiefs’ Defense Was Historically Awful. Now It’s Bailing Them Out.

Ever since Patrick Mahomes’s early season slump, NFL watchers have been waiting for the Kansas City Chiefs’ high-flying offense to return. The Chiefs have averaged 25.3 points per game this season, tied for 13th — which isn’t bad. But after three straight years of finishing between first and sixth, the preseason Super Bowl favorites are well off their usual pace. They’ve scored 22 points or fewer in four of their last five games, including Sunday’s game against the Denver Broncos.

But 22 was enough to win by 13.

The Chiefs defense held the Broncos to 9 points — just like it held the Cowboys to 9 points the game before, the Raiders to 14 before that and the Packers to 7 before that. Kansas City’s defense has been playing so well lately that despite its offense averaging just 22 points over their last five games, the Chiefs have gone 5-0.

But wait, isn’t the Chiefs defense bad? “Really bad”? “Historically bad”? Well, they were:

That stayed true through Week 7, when an embarrassing 27-3 loss to the Tennessee Titans finally made the problems too big for the Chiefs — and the entire football landscape — to ignore. After a game in which Ryan Tannehill ran through the Kansas City defense and hit a “jumpman” pose in the end zone, the Chiefs ranked at or near the bottom of the league in most defensive stats and metrics. 

But since that game, they’re at or near the very top: They’re among the top three in points allowed, defensive EPA, defensive efficiency, third-down conversion rate and red-zone defense, according to ESPN’s Stats & Information Group.1

The Chiefs defense has turned into a different unit

Defensive metrics by segment of the 2021 season for the Kansas City Chiefs and leaguewide rank in those metrics

Weeks 1-7 Weeks 8-13
Metric Rk Total Rk Total
Opponent points/game 27 29.0 2 11.2
Defensive efficiency 31 22.11 3 75.71
Defensive EPA/game 32 -10.27 3 6.17
Opponent Total QBR 31 68.2 4 31.7
3rd-down conversion rate 30 48.7% 1 25.8%
Red-zone efficiency 28 73.1% 3 36.4%

Source: ESPN Stats & Information Group

And it’s not just that the Chiefs are playing weaker teams. After Week 7, Kansas City’s defense ranked 31st (18.5 percent) in Football Outsiders’ Defense-adjusted Value Over Average (DVOA), which adjusts for opponent strength. It currently ranks 14th in weighted defensive DVOA (-2.2 percent), which considers recent games more heavily than ones from the beginning of the year. This five-game stretch of elite play has dramatically improved the unit’s other seasonlong numbers; it’s now eighth in total per-game points allowed.

But how did the Chiefs and defensive coordinator Steve Spagnuolo do it? An entire unit going from nearly-worst-to-nearly-first overnight, in the middle of the season, without any personnel additions seems all but impossible.

Much of Chiefs fans’ early season frustration was directed at safety Daniel Sorensen, whose mistakes made headlines. But Spagnuolo refused to make him a scapegoat, even after a particularly bad day against the Buffalo Bills in Week 5 — one in which he registered a brutal 32.3 Pro Football Focus grade on 57 snaps.

“It’s not about one guy,” Spagnuolo told the Kansas City Star. “We haven’t been good, that’s a true statement. To focus on one person, I don’t think is fair.” But even though Spagnuolo hinted at Sorensen’s ability to make plays that fans wouldn’t necessarily see on TV, the coaches’ film  couldn’t have looked much better. After averaging 65.2 snaps over the first five games, Sorensen played only 19 snaps against Washington and 16 against Tennessee. 

2019 second-round pick Juan Thornhill, who had his snaps cut after Week 1 to much outside confusion, was called back into service. He earned a 78.1 overall grade on 59 snaps against Washington and has played at least 50 snaps every game since. He’s got the highest PFF coverage grade of any Chiefs safety at 74.9, and he’s Kansas City’s second-highest-graded defensive back.

Illustration of a football.

Related: Our 2021 NFL Predictions

The top coverage grade goes to Rashad Fenton (86.5), a third-year corner who played only 40 snaps in the first two weeks combined. He has worked a starter’s load ever since — and he’s currently PFF’s eighth-highest-graded defensive back. The improved play of the secondary as a whole has also buoyed second-year cornerback L’Jarius Sneed. PFF repeatedly dinged Sneed with mediocre-to-bad coverage grades in the first half of the season, but since his 29.3 stinker against Tennessee, he’s averaged a coverage grade of 71.1.

The return of fourth-year corner Charvarius Ward from a quad injury has provided another boost. Ward played 131 snaps across the first two games, then didn’t see action again until the Titans game. From then on, he has played an average of 55.5 snaps per game and earned an average PFF overall grade of 69.3.

But how did Thornhill, Fenton and Ward get so many more snaps? Turns out that Spagnuolo is also using his young defensive backs differently. Over the first seven games, according to ESPN’s Stats & Information Group, the Chiefs used the nickel package on 42.5 percent of defensive snaps, less often than all but one other team (the Dolphins), while setting up in dime the sixth-most often (21.8 percent). Since then, they’ve used nickel even less often (38.3 percent of snaps), and dime even more often (37.3 percent) — the second-heaviest dime use of any team across that stretch. The Chiefs are putting a sixth back on the field more and more.

With all these young defensive backs playing better and more frequently, Sorensen is playing better, too. He’s played a part-time role since Week 8, averaging 29.6 snaps per game — and his grades have gradually improved. His exclamation-point pick-six against Denver is the perfect symbol of Spagnuolo getting much better play out of his secondary just by reshuffling players.

Going into Week 8, the Chiefs were 3-4 and looked well off the pace in the AFC. Now they’re right back where we thought they would be: atop the AFC West, neck-and-neck with the Titans and Ravens and a half-game behind the Patriots for the No. 1 seed. FiveThirtyEight’s Elo predictions rank the Chiefs No. 5 overall — with a 90 percent chance to make the playoffs, 60 percent chance to win the division and 10 percent chance to win the Super Bowl.

If they do complete the full arc — title favorites, basement-dwellers and back — some might try to spin a narrative that the Chiefs were never really in trouble. But the Chiefs’ defensive reshuffling has saved their season.

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  1. Through Week 13.

Ty Schalter is a husband, father and terrible bass player who uses words and numbers to analyze football. His work has been featured at VICE, SiriusXM and elsewhere.