One of the most distinct themes from the Buffalo Bills 2025 season was the regularly striking difference in the club’s defense in the first half of games compared to the second half of games.
The Bills were simultaneously disappointing out of the gates in contests and outrageously good at making second-half adjustments in the locker room.
While those second-half adjustments were encouraging, they were often desperately needed. An under-discussed priority for Buffalo’s new defensive coordinator Jim
Leonhard is starting faster so the Bills don’t need seismic improvements after halftime to stay in games late.
Said third and fourth quarter adjustments were across-the-board improvements in essentially every classic and advanced metric for the Bills defense.
Let’s start with a look at the traditional metrics (regular season):
Data courtesy of SumerSports.com
Fewer plays allowed — more punts, fewer sustained drives — significantly fewer yards, and that yards-per-play difference is massive. For perspective, that 5.75 yards-per-drive allowed in the first half would’ve placed between the Baltimore Ravens and Chicago Bears a season ago (8th and 9th best in the NFL, respectively).
The 5.15 yards-per-play average would’ve ranked between the Arizona Cardinals and Houston Texans (21st and 22nd, respectively).
As a pass defense, the Bills went from allowing 5.97 yards per pass in the first half of games, which would’ve ranked between 4th and 5th-worst — to 5.59 per pass in the second half (between 22nd and 23rd).
As for the heavily criticized run defense, in yards-per-carry surrendered, Buffalo’s first-half efforts would’ve been the worst in the NFL by a wide margin (5.53 vs. 5.3 as actual full-game worst, Giants). Its second-half efforts would’ve ranked the Bills run defense between the 8th and 9th worst in the NFL.
How about in the sacks and turnover departments?
It doesn’t matter which metric you pinpoint — the Bills were noticeably worse in the first two quarters of games during the 2025 regular season than they were in the second half of contests.
And if advanced stats — we can call them analytics — are your thing:
Ready for the context here? And, remember, with EPA for defenses, a negative number is better.
That 0.061 Expected Points Added Per Play allowed by the Bills defense in the first half of games last season was slightly worse than the Detroit Lions offense, which had the 8th-best EPA per play in football a year ago.
The second half defense morphed the opposing offense into somewhere between the Houston Texans and Arizona Cardinals offense.
The same theme bore out in Buffalo’s two playoff games last January. The team allowed 1.12 fewer yards per play — an enormous dip — which included 6.83 yards per rush surrendered in the first half against the Jacksonville Jaguars and Denver Broncos compared to 3.05 yards per rush in the second half of those games.
Of course, these numbers do speak to the resiliency of the Sean McDermott defense, particularly last season. It was an imperfect unit that somehow summoned superpowers after halftime following typically dismal performances in the first two quarters. Those superpowers absolutely helped the Bills climb back into games — they trailed at halftime in nine of 17 regular-season contests — or hold onto leads.
Facing a second-half deficit in more than half the regular season games — 52.9% to be exact — was simply not good enough for a team that justifiably had Super Bowl aspirations.
(For the record, the Patriots were only trailing at the half in one regular-season game last regular season. The Seahawks were trailing at the half in five regular-season games.)
Of course, Josh Allen is capable of mounting second-half comebacks (and ultimately winning the game). He’s done so a whopping 12 times to date in the NFL, which is one more time than Patrick Mahomes has accomplished that feat.
There’s just too much parity in the NFL today — being down at the half and expecting a comeback win is a dangerous game, which the Bills experienced in 2025. They trailed entering halftime in the divisional-round loss to the Broncos.
Over the past three regular seasons in the NFL, the team trailing at halftime went on to win just 23.2% of the time. Last season, the Bills won four of nine games in which they trailed at the half (44.4%).
While last year’s second-half defensive heroics were undoubtedly admirable, the best blueprint for Buffalo is for Jim Leonhard’s unit to play much more soundly in the first half of games. Fast starts need to be a point of emphasis for this new iteration of the Bills defense.
