Even after an offseason’s worth of reflection, the 2015 Bills still don’t make any sense. When Rex Ryan was hired as Buffalo’s head coach that January, he inherited a defense that was loaded with talent and had finished second in the NFL in DVOA the previous season. Pairing Ryan — whose defenses had ranked among the top 12 in DVOA in five of his six years with the Jets — with players like Marcell Dareus, Mario Williams, and Kyle Williams seemed like a dream come true for anyone who loves quarterback destruction.

“Fourth in the league [in total defense in 2014] is probably a little disappointing, to be honest with you, because that’s not where my expectations are,” Ryan said during his introductory press conference. “I know we’ll lead the league in defense. That’s just the way it goes.”

Sixteen games later, the Bills went 8–8, right in the range many expected — but the way they got there was completely backward. The offense, quarterbacked by a career backup and entering the season with a slew of question marks, finished 10th in DVOA and dragged Buffalo to respectability. The vaunted defense proved to be a leaky mess, especially relative to expectations. The Bills were 24th in the league in DVOA, a tumble of 22 spots from the season before.

The optimistic view was that, by virtue of talent alone, a performance like that couldn’t happen again in 2016. With a few small tweaks, this Bills defense could get to within spitting distance of the 2014 group. After a month of nothing but awful news, though, it’s beginning to feel like the unit’s best days may be in the past.

Marcell Dareus’s 2014 campaign was ridiculous. Despite playing a healthy amount of nose tackle and consistently encountering double-teams, the 6-foot-3, 319-pounder finished the season with 10 sacks and an additional 11.5 hits and hurries, all while anchoring a formidable run defense. His All-Pro campaign was enough to earn him a mammoth contract: six years, $96.6 million with a staggering $60 million guaranteed. That’s Ndamukong Suh money, shelled out not for one of the NFL’s best defensive tackles, but for one of the game’s best defensive players overall.

Dareus played reasonably well last year, particularly against the run, but he wasn’t anywhere near the full-fledged superstar he was two seasons ago. He recorded just two sacks and 13 hurries, and Buffalo’s defense suffered as a result. With Dareus largely held in check and Kyle Williams forced to miss the final 10 games of the season after suffering a knee injury that required surgery, the Bills’ interior pass rush lacked the pop that it’d had under coordinator Jim Schwartz, who helped the unit lead the league with 54 sacks in 2014.

Kyle Williams’s absence and Dareus’s decrease in production triggered a domino effect for the rest of the front four. Mario Williams wasn’t shy about voicing his complaints with Ryan’s defensive system, but his claims that he was forced to drop into coverage too often don’t seem to hold water. What could have annoyed him was a different development: Losing Kyle Williams inspired the Bills to play Mario Williams inside more than he had at any point in his career. The fastest way to piss off a former no. 1 overall pick with a $19.4 million cap hit who’s coming off a 14.5-sack season is to make him deal with guards while Manny Lawson — who has 24.5 sacks in his career — gets to rush the passer cleanly.

In trying to find what ailed the Bills defense last year, that idea — players weren’t able to fill the roles and execute the concepts they knew best — is a good place to start. Under Schwartz, the Buffalo approach was relatively simple: It rushed the Williamses, Dareus, and Jerry Hughes, and played a pretty standard combination of man and zone behind it. Simple has never been a word used to describe Ryan’s defenses. With the Jets — who lacked edge talent throughout his six-year tenure — Ryan created pressure through scheme, rather than through individual players’ pass-rush skills.

In 2014, when Buffalo boasted maybe the most fearsome pass rush in football, it blitzed on only 20.6 percent of plays, per Pro Football Focus — significantly less than league average. Last season, that figure jumped to 32.4 percent. PFF’s splits show off an even more dramatic difference. On third downs in 2014, the Bills rushed four on 62.3 percent of their plays; on third downs last fall, that number dropped to 41.7 percent.

Whether it was a tendency to stick with old habits or a lack of faith in his personnel, Ryan was hesitant to trust his front four to bother quarterbacks on their own. There are plenty of defenses that thrive when blitzing — the Cardinals and Jets, for example — but for teams with elite pass rushers, rushing four and keeping extra bodies in coverage is a tried-and-true method for success. The problem now is that even if the Bills wanted to simplify their approach and let their fearsome foursome do most of the work in 2016, that option has vanished, at least for now.

Buffalo cut the disgruntled Mario Williams in March, and his replacement — first-round pick Shaq Lawson — is expected to open the season on the PUP list after undergoing shoulder surgery in May. Dareus, already facing a four-game suspension for his second violation of the league’s substance abuse policy, announced plans to check into a rehab facility last week. That leaves half of the spots that drove Buffalo’s 2014 defense vacated.

The Bills’ salary-cap issues have left their roster with very little margin for error, and after general manager Doug Whaley spent his first three 2016 draft picks on defensive studs out of college football title contenders — Lawson from Clemson, linebacker Reggie Ragland from Alabama, and lineman Adolphus Washington from Ohio State — the Bills desperately needed early contributions from all three. Only that can no longer happen: On top of Lawson’s injury, Ragland was lost for the season to a torn ACL in his left knee.

Like Lawson, Ragland was expected to step in for one of the formative 2014 players who fell off last season. Nigel Bradham (who signed with the Eagles this offseason) looked like a budding star two years ago, but struggled in his first season playing under Ryan. So now, instead of having two promising rookies to possibly give Buffalo a jolt at important spots, the team is likely to test out veteran retreads, such as Lorenzo Alexander and Zach Brown.

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There’s a best-case scenario for this version of the Bills, and strangely enough, it looks a lot like the teams Ryan coached with the Jets: built on great secondary play and a heavy dose of necessary blitzing. Buffalo’s defensive backfield is full of young talent, although it’s difficult to imagine the strength of this group shifting from the front end to the back. Cornerback Stephon Gilmore, a top-10 pick in 2012, has been brilliant in stretches, but he’s constantly been plagued by health issues. Gilmore hasn’t played 16 games since his rookie campaign in 2012 and missed four games last season. If he can stay on the field, though, a corner combination of him, 2015 second-round steal Ronald Darby, and nickelback Nickell Robey could emerge as one of the league’s best.

Still, that kind of thinking is dangerous. A secondary is often only as good as its pass rush, and that’s the rub: With Dareus and Lawson gone for the foreseeable future, and with Kyle Williams fresh off knee surgery and his 33rd birthday, it’s tough to envision Buffalo generating much pressure without sending a bunch of extra rushers and leaning on its defensive backs. And that’s without even mentioning the outlook for the run defense, which was 30th in DVOA last year with Dareus in the lineup.

It’s a strange feeling. Last year, the challenge was finding reasons why the Bills wouldn’t be as good as we thought; now, there’s a franticness to explain why they won’t be as bad. With most teams, we’d likely concede that they don’t have the personnel or the scheme and move on. But given Ryan’s track record and this unit’s dominance in 2014, it just wasn’t supposed to go like this. Within a year, it already feels like all of the excitement surrounding the Bills defense is gone.