Bills 3-4 reset under Leonhard: Buffalo’s multi-million dollar question before April

For nearly a decade, the Buffalo Bills' defensive identity was as predictable as a lake-effect snowstorm in January. Under Sean McDermott, 'One Bills Drive' was the cathedral of the 4-3 base and the "big nickel" sub-package.

But on Thursday, new defensive coordinator Jim Leonhard didn't just open the doors to that cathedral; he began knocking down the walls.

In a candid, 30-minute introductory press conference, Leonhard laid out a vision for a defense that is "attacking, not reactive." For a fan base accustomed to a front four doing the heavy lifting while the back end played umbrella coverage, the shift is seismic. Leonhard is bringing a 3-4 alignment -- three down linemen and four linebackers -- a move that signals the most significant schematic pivot in Buffalo since the Rex Ryan era.

However, with the NFL Draft looming in April, Leonhard’s arrival creates a high-stakes puzzle for GM Brandon Beane. The biggest question Buffalo must answer before the first card is turned in? Does this roster actually have the personnel to play "Leonhard-ball," or is a total front-seven liquidation imminent?

Taking Back the Initiative

Leonhard’s philosophy is rooted in a refusal to counterpunch, influenced by his time under Vance Joseph in Denver and his years at the University of Wisconsin. He wants to dictate terms.

"We're going to be an attacking defense up front and in the back end," Leonhard said.

"I am big on flexibility and being able to play to your best players and force offenses to try to find your issues... not always being reactive."

The stats back up the need for a spark.

Since 2023, the Broncos (under Joseph and Leonhard) blitzed at a 35.9% rate, the fourth-highest in the NFL. During that same window, Buffalo ranked 29th, blitzing just 22.9% of the time. Leonhard’s 3-4 is designed to close that gap, utilizing outside linebackers who can pivot from dropping into coverage, to screaming off the edge to create havoc in a heartbeat.

The Personnel Pivot

The transition to a 3-4 isn't just a change on a whiteboard; it’s a change in the physical profile of the players required. In a traditional 4-3, defensive ends like Greg Rousseau are atypical edge setters with elite size and length to force things back inside. In Leonhard’s 3-4, those players often have to transition to rush linebackers or 5-tech (outside shoulder of the OT) defensive ends.

Leonhard was quick to praise the versatility of the current roster, specifically pointing out corner Christian Benford and safety Cole Bishop. He called Bishop a "jack of all trades" who mirrors the way Leonhard played the position himself. But the real challenge lies in the trenches.

A 3-4 requires a massive, space-eating nose tackle to occupy blockers -- a role Buffalo hasn't prioritized in years. While Leonhard mentioned building around "known commodities," the team has already made structural changes to accommodate the new look, hiring separate coaches for inside and outside linebackers for the first time in 2026.

The "Aggressive, Not Reckless" Mantra

A sticking point for Buffalo has been a pass rush that disappears when the temperature drops -- the Bills ranked a mediocre 19th in sacks over the last two seasons. Leonhard’s solution? A "week-to-week" evolution.

"There's a right and a wrong way in my opinion on how to attack quarterbacks," Leonhard explained.

"You have to try to change the comfort level of that quarterback; you’ve got to be able to speed him up, you’ve got to be able to slow him down."

To get to those passing downs, Leonhard remains a firm believer in the old-school tenet: By utilizing three big-bodied linemen to control the interior, he hopes to force offenses into predictable, long-yardage situations where his unrelenting identity can truly be unleashed.

The Road to April

As Leonhard locks himself in a room with Beane, HC Joe Brady, and the scouting staff this month, the clock is ticking. The Bills are currently projected to be over the salary cap, meaning the draft is their primary tool for reshaping the defense.

The vision Leonhard shared with the scouting department this week reportedly included a list of "no-goes" -- player traits that simply won't fit his high-communication, high-intensity system. If the Bills can't find a true nose tackle or a twitchy, stand-up outside linebacker in free agency, the draft becomes a mandatory hunting ground where they currently have seven picks to use at their disposal.

Leonhard isn't asking for patience, but he is asking for respect.

"We don’t deserve their respect right away, you’ve got to go earn it," he said of his new players.

If he can translate his philosophy into results, he won't just earn the respect of a locker room, he'll have the keys to a defense that can take over a football game.