It took a bit longer than Buffalo Bills fans may have hoped, but the defense, and namely the defensive line, is finally beginning to gel.
In the first seven games of the season, the Bills were allowing 5.95 yards per carry, the most in league history through seven games. They have since improved their average to 4.91 YPA, which is still the second-worst average in the league, but over the past four games, the Bills are allowing a league-best 3.14 YPA.
A statistical swing this big hasn't been seen since the Great Depression.
We've looked into the resurgence of defensive end Mario Williams, but how have they done it as a team? Let's take a look back at the past four weeks of film and see where they've improved the most.
The Bills' gap discipline has not been great all season, but they've started to get it right recently.
Take their game against the Titans, for example. Of course, a bulk of the damage was done on a handful of plays, but the Bills had some chances to get stops that they missed because of bad gap discipline.
That was the case on Chris Johnson's 83-yard touchdown run.
This is a play that gets stuffed for a three- or four-yard gain at the most if the linebackers are in position to make the play.
Instead, linebackers Nick Barnett and Kelvin Sheppard come up and over-pursue, getting out of their lanes. That makes it ridiculously easy for just about any back to cut back and get a lot of yards.
Against Chris Johnson, though, the mistake proves lethal.
In the above frame, there isn't a single defender with even a remote chance to make the stop besides safety Jairus Byrd, who took a bad angle (should have gone purple, went orange instead) and clearly didn't compensate for Johnson's lightning-quick burst. No wonder he went untouched.
That's not happening as much anymore.
On this play, defensive tackle Marcell Dareus does a great job of holding his ground and staying in his lane. There wasn't much upfield penetration from the defensive line, but because Dareus stood his ground, he was able to make the tackle at the line of scrimmage.
He keeps his eyes up and in the backfield, and once he sees the run is headed his direction, he tosses the offensive linemen to the side and makes the play.
Creating disruption in the backfield is a great way to create negative plays in the running game or get stops for no gain. The Bills defensive line was getting blown off the ball earlier in the year, allowing big holes for the backs to run through.
They gave up 247 rushing yards to the Patriots, in part because of New England's quick-hitting running game but also because they were simply getting moved off the ball.
On 1st-and-10, the Patriots lined up with three wide receivers, a tight end and running back Brandon Bolden. Rob Gronkowski shifted into the backfield to seal the edge.
Bolden initially took the handoff to the left side, but after getting a read on the offensive line, he cut it back. This was made possible because the line had pushed upfield, giving him more of an opportunity to run the other direction when he saw the unblocked linebacker headed toward the initial hole.
With that, he shifted gears, changed directions and found the hole behind the lead blocker. He used his downfield blocks well and made a defender miss on his way to a 27-yard scamper.
When the defensive line is getting penetration and holding its gaps, though, this is a different unit.
Kyle Williams has been the best and most consistent defensive linemen for the Bills this season because of his versatility in maintaining gaps and penetrating upfield.
On this running play against Jacksonville, he did both at a high level. Everyone in the stadium knew it would be a running play, but what direction was the question.
Kyle did a great job of standing up the offensive linemen in front of him, keeping his eyes in the backfield to get a read on which way the play is going while also pushing upfield.
Because of that, combined with a nice job by defensive ends Kyle Moore and Mario Williams of setting the edges, Jaguars running back Rashad Jennings is stopped for a one-yard gain.
The Bills built their defensive line around their ability to hold their gaps, but they are more than capable of getting penetration and disrupting plays in the backfield and at the line of scrimmage.
Sometimes, it's as easy as blocking and tackling.
Linebackers were getting blocked at the second level—partly because of bad reads on their part, and partly because of the defensive linemen getting taken out of the play—allowing 49ers running backs to go for long gains at the second level.
Take this play, on 1st-and-goal from the 8-yard line.
The Bills know it's a running play, with the safety creeping into the box.
The linebackers get blocked out of the play almost immediately at the handoff, and all Gore had to do was weave his way through the traffic.
Were it not for a superlative effort from Kyle Williams to get off the block and chase down the play from behind, Gore might have scored the touchdown.
Because of the improved play up front, the Bills linebackers are in a better position to make plays of their own.
Against the Dolphins, the linebackers played a big part in run defense, specifically on this play.
It's rather unspectacular on the stat sheet, just a tackle on a three-yard gain, but it is an example of execution in run defense unlike what we saw from Buffalo earlier in the season.
The defensive line did a great job of holding their spots, allowing all three linebackers to roam free and find the holes to plug. Nick Barnett and Da'Norris Searcy teamed up to bring Dolphins running back Daniel Thomas down for a two-yard gain.
Building Toward a Finished Product
If this exercise has taught us one thing, it should be that run defense is a team effort, but that one player can make a huge impact, positive or negative, that could make the effort of the other 10 players meaningless on any given play.
The Bills defense is staffed with a lot of new personnel, and it's also coached by a new defensive coordinator. Learning a new scheme and trying to come together with new faces all at once can be tough.
The early results were not good. The latest results offer some hope.
That being said, the early results came against top-notch rushing attacks like the Patriots, 49ers, Titans and Texans (and had tough days against the likes of the Chiefs and Cardinals, too). Their recent results have come against the Jaguars (who were without Maurice Jones-Drew), Colts and Dolphins (and a markedly improved performance against the Patriots).
All that being said, the Bills are fundamentally better in run defense. Where they go from here will be a product of how they build on that success.
Erik Frenz is the AFC East lead blogger for Bleacher Report. Be sure to follow Erik on Twitter and "like" the AFC East blog on Facebook to keep up with all the updates. Unless specified otherwise, all quotes are obtained firsthand or via team press releases.