The Buffalo Bills have switched back and forth between a 3-4 and a 4-3 defense several times in recent years. Now that the 3-4-minded Mike Pettine has left his post as Bills defensive coordinator and has been replaced by the 4-3-minded Jim Schwartz, another scheme switch could be in the works.
That means shopping for new pieces to fit the defense. At present, the Bills only have two players locked into starting roles at linebacker, and if they want to fortify their base defense, they'll need a third.
To know what to shop for, though, it helps to start by taking stock of what the Bills already have in place.
The most notable piece, of course, is Kiko Alonso. The Bills drafted him last year with a second-round pick and immediately made him the starting inside linebacker. His athleticism and big-play ability shone through time after time on his way to 159 total tackles (87 solo, 72 assists, 11 tackles for loss), two sacks, four interceptions, five pass breakups, a forced fumble and two fumble recoveries.
That high level of athleticism has led some to believe that he could play either inside or outside in a 4-3 defense, potentially moving over to the weak-side linebacker position, where his abilities in coverage would be put to best use.
Alonso's versatility is a big bonus for the Bills, as it allows them to focus less on what positions they need to fill and more on simply finding the best linebackers available to execute their scheme.
Could one of those linebackers be Manny Lawson? The Bills signed Lawson to a four-year, $12 million deal last offseason, so he's clearly in the plans on some level. Lawson is considered a strong-side linebacker, so if there's one specific position the Bills are set, that's it.
With that, we're looking at potential fits for the Bills on the weak side and in the middle, depending on where they decide to put Alonso.
Khalil Mack, Buffalo
Khalil Mack is the hometown product that Bills fans will lust after this year. He is projected to be a top-10 pick, so the Bills may not even get the opportunity to make the theoretical hometown story into a reality.
Mack lines up mainly on the edge, but according to CBS Sports' scouting report, he has a "versatile skill-set and has experience lining up all over the front seven." He lined up in either a two- or three-point stance on the edge, allowing him to use his unique blend of power and speed to get after the quarterback or set the edge in run defense.
One problem with Mack's potential fit in Buffalo is that he is not considered a highly effective coverage linebacker. His range and instincts in that role both leave something to be desired. Those are important aspects to playing the weak-side linebacker spot in a 4-3 defense, but his talent in other areas could lead to him being used in a similar way to Von Miller with the Broncos.
He's also "not the most consistent tackler in space," according to CBS Sports, which could be trouble for his fit in Schwartz's scheme.
C.J. Mosley, Alabama
Alabama consistently turns out linebackers who get drafted in the first round, and C.J. Mosley should be no different. Mosley finished with 108 tackles in 2013, 39 more than the next-closest Alabama defensive player.
CBS Sports' scouting report says he "does a nice job using his length and lower body fluidity to keep himself clean through a crowd and finishes at the ball, wrapping and driving through his target" but that he "isn't always fundamentally consistent as a tackler."
He also earned a comparison to Buccaneers All-Pro linebacker Lavonte David for his "combination of toughness, elite instincts and superb athleticism," and he is regarded as a versatile linebacker who can line up either inside or outside. That would leave the Bills with two linebackers capable of switching positions, giving them a great deal of flexibility in that regard.
But it's not just about versatility, it's about being successful at what you do. The Bills sorely need a linebacker who can help against the run, and Mosley gives them a good boost in that area.
They've finished in the bottom five overall against the run and bottom 10 in average yards per rush in each of the past five years. They allowed 129 rushing yards per game and 4.4 yards per rush attempt last year; Mosley, on the other hand, was the anchor of an Alabama defense that allowed just 106 rushing yards per game and 3.3 rushing yards per attempt.
The Bills could do a lot worse for themselves than to grab Mosley with their first-round draft choice.
Shayne Skov, Stanford
No one will question Shayne Skov's physicality and instincts. He is built like an NFL linebacker at 6'2" and 245 pounds. He knows how to use his frame to shed blocks and is considered a tone-setter for his temperament in attacking the ball-carrier.
Every player has flaws, but as you start to get into the later rounds, the number or importance of those flaws will likely increase. For Skov, the flaws are easy to spot: a lack of speed and overall athleticism, which leads to some aggressive overpursuing of runners when he tries to compensate.
Like the Jets' standout inside linebacker, Skov's value lies with his instincts and physicality, especially as a run-stuffer. He's a fiery competitor who will quickly emerge as a fan favorite, even if his lack of ideal athleticism limits his role.
The Bills may feel safe plugging Alonso in at the weak-side 'backer spot, with Lawson on the strong side, which would open up the middle for a two-down linebacker like Skov.
Chris Borland, Wisconsin
Chris Borland is described as a "heady, passionate player" by CBS Sports but is knocked for his "pedestrian size and athleticism" at 5'11.75" and 245 pounds with short arms around 28.625" inches long. That combination may scare off some scouts, but it was good enough to land him 420 career tackles (50 for loss), 17 sacks and three interceptions.
His best fit would be in the same spot he spent his college career, playing inside in a 4-3 or a 3-4 defense. He doesn't have the ideal speed for a sideline-to-sideline 'backer, but he has a high motor that makes up for it at times. Rightfully, there are questions as to whether he can continue making effort plays in the NFL, where his lack of athleticism could be magnified more so than it was in the Big Ten.
His sharp instincts will also help him make those plays, allowing him to be in the right place at the right time. He has earned comparisons to Dolphins linebacker Zach Thomas for all those qualities.
If the Bills are comfortable sacrificing some athleticism for football smarts, they could justify using a third-round selection on Borland.