The Bills came out of 2025 with the same story they always seem to tell: another top-two offense powered by Josh Allen, another January that didn't end in a parade.

Table of Contents

1. The macro picture: pass defense fine, run defense a mess
2. Where the run damage actually lives: up the middle and right guard
3. The short-yardage collapse
4. What didn't change: edge runs and explosives
5. Why this matters

The macro picture: pass defense fine, run defense a mess

Start with the season-level EPA splits. In 2024, Buffalo's defense allowed -0.065 EPA per rush. In 2025 it allowed +0.085 EPA per rush — a swing of roughly 0.15 EPA/play on the ground and the 4th-worst run defense EPA in the league. The pass defense, meanwhile, barely moved in the wrong direction and, if anything, got better: -0.091 pass EPA/play, good for 9th in the NFL.

So the "Buffalo can't stop anybody" narrative isn't quite right. The pass-rush-and-coverage side of the ball is roughly a top-10 unit. The run defense is the problem, and inside the run defense the damage is concentrated in a very small number of places.

Where the run damage actually lives: up the middle and right guard

Break the runs Buffalo defended by direction. Edge runs (left end + right end) actually got worse in raw yards per carry but were already a leak in 2024, so they didn't change the story. The interior — anything at guard, tackle, or straight up the middle — is where the season turned.

Runs up the middle against Buffalo:

A full yard per carry, a 0.20 EPA swing, and the stuff rate cut nearly in half. That's not variance; that's a front that isn't winning at the point of attack.

The right-guard gap tells the same story even more sharply. In 2024 runs off right guard were arguably Buffalo's best defensive gap on the field:

Roll interior runs together (middle plus guard/tackle on either side) and the picture is clean: 373 attempts, 4.85 YPC, +0.064 EPA/play in 2025, versus 348 attempts, 4.41 YPC, -0.075 EPA/play in 2024. Same volume, dramatically worse outcomes.

The short-yardage collapse

If interior runs are the mechanism, short yardage is the scoreboard. Filter to rushes on 3rd or 4th down with 1 or 2 yards to go — the exact down-and-distance where a real defensive front decides drives.

In 2024 Buffalo let opponents convert short-yardage runs at 63.6% (5th-best in the league by conversion rate, mid-pack by EPA). In 2025 that jumped to 83.7% — 30th-best (3rd-worst) — and the EPA cost of those plays exploded to +0.544 per attempt, the third-worst mark in the NFL among teams with at least 15 such attempts. Opponents essentially had a green light: line up, get behind the right guard, get the sticks.

That's the sentence that should worry Bills fans more than any Allen interception. On the small handful of downs each week that most directly determine whether a drive lives or dies, Buffalo went from a top-third defense to bottom-three.

What didn't change: edge runs and explosives

The other tell that this is a specific problem — not a general one — is what didn't move.

• Explosive-run rate (runs of 10+ yards allowed) went from 15.55% in 2024 to 15.37% in 2025. Essentially flat. Buffalo isn't giving up more chunk plays; the sky-high YPC on interior runs is coming from consistent 4-to-6-yard gains, not blown gaps.
• Edge runs (left/right end) went from 151 attempts at 5.48 YPC / +0.13 EPA in 2024 to 111 attempts at 6.64 YPC / +0.21 EPA in 2025. Worse per carry, but on 40 fewer attempts — offenses noticed the interior was easier and moved their volume there.

Coverage numbers are steady. The pass rush's contribution shows up in the pass EPA figure (9th). This isn't a "the whole defense fell apart" season. It's a run-fits and interior-front problem, exposed most brutally when the game shrinks to 1-2 yards.

Why this matters

A team built the way Buffalo is built — elite quarterback, top-two offense (+0.138 EPA/play, 2nd in the NFL in 2025), competent pass defense — has one obvious way to lose in January: give the ball back on 3rd-and-1, give up the clock, and force Allen into hero-ball late. That's exactly the failure mode a defense ranked 3rd-worst in short-yardage EPA sets up.