Through the first few weeks of the season, the Buffalo Bills looked like they had one of the NFL's best defenses. Even accounting for their dispiriting loss to the New York Jets in Week 1, the Bills put together a quartet of fantastic defensive performances in Weeks 1 through 4. 

They allowed a total of just five points to the Jets, Las Vegas Raiders, Washington Commanders and Miami Dolphins, and they checked in fourth in TruMedia's EPA/play and second in FTN's DVOA (Defense-adjusted Value Over Average). They were getting a strong pass rush despite the absence of Von Miller, and they had even better coverage on the back end. 

But beginning with Tre'Davious White's Achilles tear in Week 3, the Bills have been hit with a spate of bad lack, and it could have a dramatic effect on their defense the rest of the way. With White already out, Buffalo also lost linebacker Matt Milano and defensive lineman DaQuan Jones to injured reserve. Milano and White might be the two best players in Buffalo's back seven, and Jones is a valuable rotational defensive lineman. 

This week, edge rusher Greg Rousseau and cornerback Dane Jackson have been on the injury report, while Taron Johnson got banged up in London last week as well. The Bills have resorted to signing 35-year-old Josh Norman to the practice squad to provide depth in the secondary, and they seem likely to add a linebacker at some point as well. They had already lost Tremaine Edmunds in free agency, but having Milano was a backstop against any backslide at the position. Now, Milano is out, and the Bills are left with inexperienced players (2022 third-round pick Terrel Bernard, 2023 third-rounder Dorian Williams) and street free agents at the position.  

They have a bit more second-level versatility this year thanks to their having returned both of their All-Pro safeties (Jordan Poyer and Micah Hyde) to the lineup, while also bringing back Damar Hamlin and signing Taylor Rapp. But Buffalo already spends most of its time in nickel and dime looks; and loading the field with even more defensive backs could create problems in the box -- especially without Jones occupying bodies up front. 

The Bills made a change this offseason by replacing departed defensive coordinator Leslie Frazier as the defensive play-caller, with head coach Sean McDermott assuming those responsibilities. Having a different person at the controls results in pressing different buttons every once in a while, and and McDermott has subtly tweaked Buffalo's coverage schemes this year by playing less man and less quarters, with more Cover-2 and more combination "quarter-quarter-half" coverages, according to TruMedia. He's also dramatically reduced Buffalo's blitz rate, which is down to just 19.1%, after being as high as 34% back in 2020.

The Bills will need to count on that defensive front to generate pressure without the benefit of having extra rushers, because they're going to need extra bodies on the back end now that they are dealing with a bunch of injuries on the second level. Miller is back from his torn ACL and likely working his way up to speed, while Rousseau is now on his way back from the foot injury that kept him out last week. Having a supplementary pass rush is why the Bills signed Leonard Floyd this offseason, and he checks in a strong 31st in pressure rate (14.9%) out of the 214 players who have rushed the passer 50 times or more so far this year, per Tru Media. A.J. Epenesa isn't too far behind at 45th (13.6%), and Ed Oliver (13.1%) isn't, either. 

It remains to be seen if the Bills can figure out how to remain sticky enough in coverage without White. Their first-round pick in 2022, Kaiir Elam, has not lived up to expectations and has appeared in just one game this season, allowing 6 of 8 passes thrown his way to be completed and giving up 93 yards, per Pro Football Focus. Chrstian Benford, who beat Elam out for the spot in the lineup, isn't off to as strong a start to the season as the one he had a year ago. Jackson and Johnson are solid, but they ideally shouldn't be your two best corners. They're role players. It'll be up to McDermott and Co. to figure out how to maintain things, though having the benefit of Poyer and Hyde to clean things up obviously helps. 

Still, for a team that has Super Bowl aspirations, the injuries the Bills have been dealt in recent weeks are a huge blow. Perhaps they get an infusion of talent at the trade deadline. If they want to keep pace with the best of the best, they might even need one.