For almost a decade, you knew what a Sean McDermott defense was going to look like. Four-man fronts, ton of nickel, and zone coverage. Keep everything in front of you. Bend but don’t break and make the opponent put together long drives and don’t give up the explosive play.
And for the most part, it worked.
Until the Bills needed it to work against the best quarterbacks in January. Here’s a recap if you feeling like barfing.
That’s where this season becomes fascinating, because for the first time in nine years the Bills aren’t simply changing a defensive coordinator.They’re changing their defensive identity as Jim Leonhard is installing a defense rooted in a 3-4 front, replacing the 4-3/nickel structure Buffalo used under McDermott. But the important part isn’t whether there are three or four hands in the dirt.
It’s uncertainty. Who’s rushing? Who’s dropping? Where is Ed Oliver lining up? Is Greg Rousseau an edge rusher on this snap or dropping into the flat? Is Cole Bishop coming? Is Terrel Bernard coming? Is Buffalo actually playing the coverage it showed before the snap?
Leonhard has repeatedly used one word to describe what he wants:
Attack.
And after watching this defense repeatedly fail to produce the season-saving sack or turnover against elite quarterbacks, I’m ready to see something different.
McDERMOTT VS. LEONHARD
Here’s the statistical difference that really jumps out.
That’s not a small philosophical difference. McDermott generally wanted his front four creating pressure while seven defenders handled coverage. Leonhard is much more willing to make the quarterback determine where the pressure is coming from. He isn’t promising to blitz everybody every Sunday and he’s actually stressed that Buffalo will be aggressive without being reckless. That the approach will change depending on the quarterback. McDermott wanted the quarterback to remain patient long enough to make a mistake, while Leonhard wants to make him uncomfortable enough to force one.
Since 2020, one team has won the Super Bowl after switching their defensive coordinator and that’s the Eagles in 2024.
A few things about the chart
Across the chart, only 45% improved in points allowed, meaning more than half stayed flat or got worse.
Yardage showed the strongest improvement: 52% of the defenses allowed fewer yards per game in Year 1 under the new coordinator.
Takeaways improved most often among the splash-play stats. 53% increased takeaways, compared with 45% increasing sacks.
Only 35% improved in at least three of the four categories, while just 21% improved in all four.
But the ceiling for immediate improvement was enormous. Jesse Minter’s Chargers, Vic Fangio’s Eagles, Jim Schwartz’s Browns, Mike Macdonald’s Ravens and Dan Quinn’s Cowboys are examples of defenses that made significant Year-1 jumps rather than needing a full season to adjust.
WHAT LEONHARD INHERITED
The strange thing about Buffalo’s 2025 defense is that you can make completely different arguments about it depending on which statistics you use.
Against the pass?
Pretty damn good.
Against the run?
A disaster.
The Bills allowed only 2,668 passing yards, or 156.9 per game, but they surrendered 2,315 rushing yards at 5.1 yards per carry. That’s why Leonhard keeps bringing everything back to stopping the run. If Buffalo can’t stop it on first and second down, none of these exotic pressure packages matter. You can’t unleash Rousseau, Bradley Chubb, Michael Hoecht and Ed Oliver on third-and-11 when the opponent keeps facing third-and-2.
And then there was the pass rush. Buffalo finished with only 36 sacks and they weren’t incapable of creating pressure. The bigger problem was turning pressure into drive-ending plays and that’s where Leonhard has to change this defense.
The Bills do have talent on defense, but they also have some weaknesses as well..
GREG ROUSSEAU
Rousseau is probably the player I’m most interested in watching in Leonhard’s defense.
That last number might be the most impressive.
We spend so much time talking about Rousseau becoming a double-digit sack guy that it’s easy to overlook that he was already one of the best run-defending edge players in football. The pass rush wasn’t bad, either. His 55 pressures ranked 16th at the position.
The problem?
They didn’t turn into enough sacks and Rousseau has never reached double digits in a season. Leonhard thinks the new alignment will give him more room on the edge and allow him to use his ridiculous length.
BRADLEY CHUBB
Chubb gives Buffalo something it badly needed: another established pass rusher opposite Rousseau. The other edge outside of Von Miller since 2021 has been kind of blah and insonsistent. Mario Addison, Leonard Floyd, Boggie Basham, and AJ Epensa aren’t going to enter your jersey collection anytime soon.
Buffalo isn’t getting a player coming off an elite season. Chubb still generated 48 pressures, but the overall efficiency wasn’t particularly good. The Bills are betting that putting him into Leonhard’s system and not requiring him to be the pass rusher can make him more dangerous. If Rousseau produces another 50-plus pressures and Chubb gives Buffalo somewhere around 45-50, suddenly offenses have a much different protection problem.
TERREL BERNARD
Bernard’s 2025 numbers were much more concerning and we are at a crossroads.
That’s not a particularly flattering statistical profile. And that’s one of the reasons I’m so interested in seeing what Leonhard does with him. We’ve already seen Bernard be an effective blitzer earlier in his career. Yet he finished 2025 without a sack and ranked only 51st among linebackers with nine pressures. That has to change and Leonhard’s fronts should create opportunities for Bernard to attack instead of constantly reacting.
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CHRISTIAN BENFORD
Benford’s numbers are fascinating because different metrics tell completely different stories.
57 targets
31 completions
54.4% completion rate allowed
362 yards
6.4 yards per target
4 touchdowns
2 interceptions
82.6 passer rating allowed
That run-defense number is ridiculous. He’s always reminded me of Antoine Winfield with how he plays. No qualified NFL cornerback graded better against the run. His coverage grade, however, was only 87th. That’s something worth monitoring if Leonhard plans to ask Benford to play more man coverage and potentially follow No. 1 receivers. We all know McDermott wanted guys in zone for the most part The upside is that Benford has already demonstrated he can do considerably more than simply cover. He can tackle, blitz, and play physically.
That makes him extremely useful in a defense built around disguise.
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COLE BISHOP
Here’s the player whose numbers might excite me the most.
That’s the profile of a young safety who was already becoming a legitimate coverage weapon. He ranked 15th among qualified safeties in PFF coverage grade and tied for 11th with three interceptions. Now give that player to Jim Leonhard, a former NFL safety who made a career out of disguise and versatility. This might be the defender who takes the biggest jump and I don’t want Bishop standing 15 yards deep every snap. Move him everywhere!!! Deep safety, box, slot, blitz him, show the blitz and drop him.
Make the quarterback locate him before every snap.
MAXWELL HAIRSTON
This might be one of the most important players on the entire defense and also the most scrutinized. Hairston didn’t do much last year except get hurt and burned a couple times. He did have that one play where he kept up with the Chiefs’ Worthy.
Hairston has elite speed and Leonhard believes he has the traits to play man coverage. If Hairston can legitimately hold up opposite Benford, Buffalo’s entire pressure menu expands. The Bills have just 3 boundry corners on their roster tells me they are counting on him.
DEONE WALKER
Walker didn’t pile up sacks as a rookie, but that’s not really what makes him interesting.
Leonhard doesn’t need Walker chasing 10 sacks. He needs him eating blockers so Rousseau, Chubb, Oliver and Bernard don’t have to. Buffalo allowed 5.1 yards per rushing attempt last season, Walker’s development may ultimately matter more to this defense than another edge rusher adding three sacks.
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DAVISON IGBINOSUN / DEE ALFORD / JORDAN HANCOCK
This is another indication that the philosophical shift isn’t accidental. Buffalo has collected defensive backs with different body types and different skill sets. Igbinosun gives Leonhard a young physical boundary option and Alford brings veteran experience. Hancock brings versatility but he struggled when pressed into action last year. The big countdown is whether IGB eventually takes Hairston’s job, but I’m not buying it.
C.J. GARDNER-JOHNSON
Want turnovers?
Here’s your guy.
Want a head case?
See above.
He’s been on 6 teams and he wasn’t very good last year but very good the year before.
He’s definitely the guy who could be the straw that stirs the Bills Defensive drink or the straw that breaks the camel’s back. In other words, he’s very much a high-risk, high-reward player.
ED OLIVER
Maybe nobody benefits more from the coaching change.
Oliver opened 2025 with: 3 sacks in three games. He was unreal in the opener against the Ravens. Then injuries basically destroyed his season, but here’s the advanced number that really explains why Leonhard is excited about him.
Over Oliver’s NFL career, Next Gen Stats has tracked him at roughly a 38.4% double-team rate while still producing an average 11.7% quarterback-pressure rate from the interior.
That’s impressive and exactly why Leonhard wants to move him around. If an offense knows exactly where Oliver is going to line up, it can find him and double him. So stop telling them and move him all over the field.
DORIAN WILLIAMS
That completion percentage is encouraging. The touchdowns and passer rating are less so. Williams’ athleticism has never really been the question… It’s processing. I feel no one wants Williams starting and the preference is having new blood there.
MICHAEL HOECHT
Hoecht might be Leonhard’s perfect chess piece and he’s also probably the most hyped or maybe overhyped player on this roster. His 2025 season lasted only six quarters, but he immediately flashed why Buffalo wanted him.
He produced: 2 sacks 1 forced fumble
Pat Moran had to get looser fit pants to hide his excitement. Then came the Achilles injury. So this isn’t really a statistical question as it’s a health question.
How much of that player is coming back? Because if Hoecht gets anywhere close to his pre-injury form, Leonhard has a 260-plus-pound defender he can move around the formation. He doesn’t necessarily need 700 snaps as he needs to give Buffalo 25 disruptive snaps a game.
T.J. SANDERS / DEWAYNE CARTER / LANDON JACKSON
This group isn’t going to generate the headlines. I don’t have much to add for this trio except one of them has to step-up. Brandon Beane has loved him some DL and these 3 have flashed absolutely nothing. One of them put on weight this offseason. That’s all I got.
KALEB ELARMS-ORR
This is the rookie linebacker to watch by all accounts and a guy who may take someone’s job. And there’s an important distinction here: Leonhard inherited Bernard. He inherited Williams. He inherited Andreessen.
Elarms-Orr was drafted for this defense and I’m sure Leonhard had a say here.
Buffalo selected him knowing exactly what Leonhard wanted to install. If he earns meaningful snaps quickly, pay attention.
Final word
We already know Joe Brady can coach offense, but that’s not the part of his promotion that interests me. The decision that might tell us whether Brady can actually be a great head coach is the one he made on the other side of the ball.
Brady entrusted the Bills defense to a defensive coordinator who had never previously been an NFL defensive coordinator. And unlike calling plays for Josh Allen, there’s nowhere for Brady to hide if it doesn’t work. That’s one of the strange things about being an NFL head coach. You often get hired because you’re great at one thing, then ultimately get judged by everything else.
Sean McDermott is a pretty good example. He never received much credit for Josh Allen developing into one of the best quarterbacks in football. But when the Bills defense failed in the playoffs, nobody cared that McDermott wasn’t throwing the passes or missing the tackles. It was his defense. His staff. His responsibility.
Brady is about to live on the other side of that equation even if it isn’t his expertise. Leonhard is going to be the key to get the Bills over the playoff hump that Sean McDermott was fired for.
