Former Wisconsin Badgers defensive coordinator Jim Leonhard got his major break this offseason, as he was hired as the Buffalo Bills defensive coordinator under new head coach Joe Brady.
Leonhard, 43, had been with the Denver Broncos since 2024, being hired as the defensive backs coach and pass game coordinator under Sean Payton. He was promoted to Assistant Head Coach last offseason and was primed to earn a defensive coordinator role this offseason, earning several interviews for openings.
In Buffalo,
Leonhard joins one of the NFL’s most successful franchises over the last few years, and will take over a defensive unit that has a number of questions heading into 2026.
In fact, ESPN’s Ben Solak believes Leonhard might have the ‘toughest task’ of any defensive coach in the NFL this offseason, given the uncertainty around the Bills defense.
He’ll replace Sean McDermott, who had been the defensive mind in Buffalo since 2017, and will reshape Buffalo’s defense into a new look.
“Playcaller stability is famously rare in the modern NFL,” Solak wrote. “More than half of the league will have a new offensive playcaller this season. The longest-tenured offensive coordinator is the Packers’ Adam Stenavich, who has held the job (without calling plays) since 2022. Matt LaFleur, Green Bay’s head coach and playcaller, is one of only five head coaches who were hired for their current position before 2020, and all five have offensive backgrounds.
“Sean McDermott was the lone long-term head coach with a defensive background before Buffalo fired him in January. McDermott had shaped the Bills’ defensive identity since his hire in 2017. He didn’t always call plays, but the defense was unquestionably his: all nickel packages, a heavy reliance on spot-drop zone and traditional four-man rushes. As the seasons wore on and McDermott’s seat warmed, Buffalo experimented with various schematic curveballs, but the defense remained built in McDermott’s image.
“His seat is now filled by his ex-offensive coordinator Joe Brady, and the defensive side of the ball now belongs to Leonhard. Leonhard has long been considered a rising star. A longtime defensive coordinator at his alma mater Wisconsin, Leonhard was on the cutting edge of the college meta with match coverages and simulated pressures. He has worked with Broncos defensive coordinator Vance Joseph the past two seasons, studying under one of the league’s preeminent blitzers.”
Leonhard’s base looks are expected to be different than what Buffalo showed under McDermott, which could mean different responsibilities for Buffalo’s returning starters.
“Leonhard is cut from a different cloth than McDermott, from the nuances to the basics,” Solak continued. “McDermott’s defense is based out of the 4-3; Leonhard’s will base out of the 3-4. Players who only rushed the passer under McDermott will need to learn how to drop into coverage. As structure changes, technique follows. Players who primarily had single-gap responsibilities in run defense will suddenly play 1½, or even two, gaps far more often. And with these new demands come new ideal body types. McDermott loved undersized speedster linebackers such as Terrel Bernard and disciplined zone corners like Christian Benford. Leonhard might prefer different prototypes.
“These are broad strokes we’re painting with. Benford might be a more ideal fit in a different defense, but he’s a very good player, and Leonhard will adapt his defense around him. As Leonhard said of defensive tackle Ed Oliver’s role earlier this summer: the base defense might be different, but “the subpackage things are a little bit more familiar to what they’ve done here from a front structure.” There will be some crossover.
“Still, it’s hard to shift defensive gears on a roster that was so meticulously built to another person’s specializations for so long. Players like Benford and Oliver, on their second contracts, have never played in a non-McDermott defense. This will be their first time learning a new defensive language. With such a wholesale shift inevitably comes growing pains.”
The big challenge, though? Buffalo needs to contend now, which doesn’t give much time for those growing pains, and the urgency to win was only further seen by McDermott’s firing this offseason.
“But the Bills don’t have time for those pains. McDermott was fired after six consecutive seasons in which Buffalo won a playoff game. They were only the fourth team in NFL history to achieve such consistent success. But the three previous teams won nine collective Super Bowls; the Bills haven’t even been to one. The message is painfully clear — anything less than the Super Bowl is a failure.
“Leonhard doesn’t just need to install a good defense — he needs to do it fast, and with players largely selected for a different system. With the stakes and the challenge considered, I’m not sure there’s a defensive coach in the league with a tougher task this summer.”
Leonhard has a strong defensive pedigree and should get full autonomy in Buffalo, but he’ll definitely have a challenge ahead of him reconstructing the Bills defense in 2026.
