How the move to a 3-4 defense will impact the Bills and Broncos

The Buffalo Bills and Denver Broncos sported two of the NFL's best defenses in 2014, both centered around stalwart edge rushers.

But after the clubs brought in new head coaches and personnel this offseason, they'll each be shifting their base defenses from a 4-3 to a 3-4.

Here, we break down what that shift means for both the Bills and Broncos.

Buffalo Bills

The Bills ran a 3-4 scheme two seasons ago under Mike Pettine, a disciple of new head coach Rex Ryan. Although Jerry Hughes put together a breakout campaign coming off the bench, the Bills' 388 points allowed ranked 20th in the league that season.

Buffalo's 54 sacks led the NFL in 2014, and the main question this offseason is how the team will maintain its dominant pass rush while transitioning back to a three-man front. All three of Buffalo's interior linemen should have two-gap responsibilities in the new scheme, with the inside linebackers cleaning up the vacant space.

Marcell Dareus will line up at nose tackle, and with the ability to occupy two blockers comfortably, he'll be responsible for covering the "A" gaps on either side of center. Kyle Williams and Mario Williams should both see snaps at defensive end, with the latter often lining up as a stand-up outside linebacker, opposite Hughes.

Generally, two-gap defenders tend to be slower, but all three of the Bills' defenders possess excellent speed for their size, and ought to dominate in a run defense centered around Dareus's presence in the middle.

Williams has produced as a stand-up outside linebacker in the past and will be utilized in space more often along with Hughes. The 6-foot-2, 255-pound Hughes excels in coverage for a player of his size, and may be deployed against tight ends and running backs coming out of the backfield. As a result, Williams should once again be relied upon as the unit's primary pass-rush presence off the edge.

One of the core tenets of a strong 3-4 defense is having a strong middle linebacker who can track down players with excellent sideline-to-sideline speed, while maintaining discipline and tracking in coverage. The notable difference for the Bills entering 2015 is that they lack a middle linebacker with the sideline-to-sideline speed and range of Kiko Alonso.

Preston Brown's superior coverage skills will likely see him featured as the nominal weak-side linebacker. In such a role, Brown would largely be responsible for cleaning up plays while strong-side linebacker Nigel Bradham gets downhill and attacks at the line of scrimmage.

The 6-foot-1 Bradham ranked as Pro Football Focus's sixth-best pass-rushing 4-3 outside linebacker last season, and is also likely to be deployed in blitz packages.

With the NFL increasingly becoming a passer's league, there will be plenty of sub-packages involved that take the core 3-4 personnel off the field. In a nickel formation, it's imperative that the returning pass-rush group of Williams, Williams, Dareus and Hughes dominate.

Buffalo's 3-4 defense will likely be able to generate pressure from all angles, relying on the team's traditional brute force while putting a greater emphasis on the team's overall speed. It wouldn't be much of a surprise if they topped 50 sacks once again in 2015.

Denver Broncos

Wade Phillips became the Broncos' defensive coordinator in January, joining new head coach Gary Kubiak and immediately implementing a 3-4 formation. Denver ranked third in total defense last season and will likely have one of the league's elite defenses again in 2015.

In a 3-4 base scheme, Von Miller will remain the centerpiece of the defense, with his precocious pass-rushing skills on display even more often. Miller graded out as Pro Football Focus's best pass-rushing 4-3 outside linebacker in 2014, leading all players at his position with 14 sacks, 11 quarterback hits, and 47 quarterback hurries.

Miller will likely be used as a hybrid defensive end/outside linebacker, responsible for attacking the quarterback off the edge. The 26-year-old is also an outstanding run-stopper, further adding to his value on early downs.

DeMarcus Ware specialized as an edge rusher earlier in his career, and while he's lost a step, his ability to diagnose the play at the line of scrimmage is second to none.

The eight-time Pro-Bowler is much better suited to a 3-4 defense than a 4-3 because of his closing speed, and it's a good bet he'll reach double-digit sacks for the ninth time in his career. Ware will line up opposite Miller, and the Broncos duo, much like Mario Williams and Jerry Hughes, will nominally be utilized as defensive ends in nickel and dime packages.

Brandon Marshall is arguably the best coverage linebacker in the NFL, and he'll be expected to clean up plays with fellow linebacker Danny Trevathan playing more of a downhill role and often taking on opposing lineman at the point of attack.

The main difference between Buffalo and Denver's front is that the Broncos will likely be using a one-gap technique under defensive coordinator Wade Phillips's tutelage. Though he's more of an upfield penetrator, such one-gap responsibilities could see Sylvester Williams excel at the nose tackle spot.

Denver recorded 41 sacks in the 4-3, but the club is likely to improve upon its 2014 total with a scheme that will showcase Miller and Ware's outstanding pass-rushing abilities. With Marshall and Trevathan having the ability to disengage from blockers quickly and reroute onto running backs and tight ends, the Broncos' front three will merely have to focus on shedding their blocker at the line of scrimmage, and then wait for the cavalry to arrive.