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.
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.
That's not happening as much anymore.
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.
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.
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.
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.
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.
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.
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.