The nature of football doesn't lend itself to statistical analysis with the same expediency of baseball, which features a one-on-one showdown between pitcher and batter at the heart of the sport. Because all 11 teammates on both sides of the ball are inextricably linked each play, it's impossible to extract one football player's value from his surrounding talent and coaching staff.
Advanced metrics have come a long way over the past decade, partnering with game-film analysis to allow services such as Pro Football Focus, Football Outsiders and Next Gen Stats to isolate each player's contribution on a given play. Still, context is too often missing in the numbers.
What can completion percentage tell us without factoring in the degree of difficulty in terms of passing distance and defensive coverage? Why are all drops counted equally when some are meaningless blunders in the waning moments of blowouts while others cost a team dearly with the game on the line?
Measuring individual offensive contribution is tricky enough. Finding meaningful statistics to capture individual defensive dominance is an even more elusive endeavor.
Take tackles, for example. Most NFL coaching staffs tabulate tackles in a different manner than the official game charters. By the time the box score comes out, we're left to wonder how much a solo tackle is worth compared to an assisted tackle. What is the value of a tackle 10 yards downfield compared to one at the line of scrimmage?
Just as all tackles are not created equal, the same logic applies to quarterback takedowns. A third-down sack that knocks the offense out of field-goal range will show up on NFL.com carrying the same weight as a first-down tackle of a scrambling quarterback for a 1-yard loss. Swiping the quarterback's elbow to force an interception or fumble draws the same "QB hit" designation as a forced incompletion.
If a pass rusher generates a turnover on nearly half of his sacks, isn't he increasing his team's chances of winning to a greater degree than a similar player unable to force fumbles?
As long as football is played, there will be no substitute for watching the games with a discerning eye. Although I've watched at least the condensed NFL Game Pass version of every game this season (the Jets and Dolphins have been known to put me to sleep on occasion), I also understand the limitations of the exercise. How can I watch the left cornerback and the right tackle at the same time? It's simply not realistic to personally grade every player on every play, which is why I like cross-checking my biases with advanced statistics, historical anecdotes and relevant quotes from players, coaches and analysts.
The following list of Defensive Player of the Year candidates is based primarily on the eye test. For my own edification, I've also developed a big-play formula to help gauge the impact of the league's most disruptive defensive stars. To that end, I've factored in sacks + stuffs (tackling a runner or receiver behind the line of scrimmage), QB hits, QB hurries, forced fumbles, fumble recoveries, interceptions, pass deflections, touchdowns, stops (solo tackles that constitute a failure for the offense, per Pro Football Focus' metric), missed tackles, penalties and a couple of secret ingredients to come up with one composite playmaker score.
1) Aaron Donald, defensive lineman, Los Angeles Rams
A brick wall with ninja skills, Donald is essentially unblockable. The reigning Defensive Player of the Year has accounted for 48.5 percent of the Rams' 34 sacks, the seventh-highest rate in NFL history if it stands, according to NFL Research. Donald leads the league in sacks (16.5), QB Hits (34), tackles for loss (20) and disruptions (71), which factors in run stuffs and pressures. My playmaker formula gives Donald a score of 158.2 -- 20 points higher than second-place J.J. Watt. Here's what separates Donald from the pack: He offers the highest level of production while facing the highest percentage of double-teams from opposing offenses.
2) Khalil Mack, outside linebacker, Chicago Bears
After managing just 33 takeaways over the past two seasons combined, the Bears are leading the league with 35 takeaways and 107 points off turnovers this year. They are one of only four teams in the past decade to record at least 35 takeaways and 45 sacks in a season. Vic Fangio's defense is the best in the league, essentially earning its own tier in Football Outsiders' defensive metrics.
The difference this year is the presence of Mack, who opens opportunities for other players with his relentless pressure in the passing game and penetration against the run. Despite an ankle sprain that caused him to miss two games and lose his explosiveness and effectiveness in two others, he boasts a league-leading six forced fumbles on 12.5 sacks.
3) J.J. Watt, defensive lineman, Houston Texans
Andrew Luck's primary competition for Comeback Player of the Year honors has the highest motor I've ever seen. I wish we could find a way to measure how many times he beats his man only to just miss a tackle for loss. After going nearly two calendar years without a sack, Watt ranks second only to Donald with 14.5 in 14 games. He's also tied with Mack for the lead in forced fumbles while playing the run as well as any defensive end. Watt might never again reach the pre-injury heights that forced his name into MVP debates, but he's still playing at an All-Pro level as his 30th birthday approaches.
4) Luke Kuechly, linebacker, Carolina Panthers
Kuechly is coming off two of the most dominant linebacker performances in franchise history. He almost single-handedly shut down the Saints' high-octane offense on "Monday Night Football" after forcing a pair of fumbles and chasing down Jarvis Landry from behind like a madman to prevent a touchdown in Week 14. It's a shame the Panthers are falling apart around their defensive leader because Kuechly is making plays behind the line of scrimmage at an unprecedented rate. His 21 stuffs not only lead the league, but are also the most ever by a linebacker, according to research done by Pro Football Journal. For comparison's sake, fellow perennial All-Pro Bobby Wagner has managed just 3.5 stuffs this year. Don't buy into the trendy narrative that Wagner has overtaken Kuechly as football's greatest inside linebacker today.
5) Cameron Jordan, defensive lineman, New Orleans Saints
An especially dominant run defender for an alleged sack artist, Jordan carries the fourth-highest score (110.6) in my playmaker index. While Sheldon Rankins, David Onyemata and Demario Davis have emerged as impact players in their own right, Jordan is the linchpin of a suddenly stingy New Orleans defense that has carried the offense over the past month. This might just be the best defense of the Sean Payton-Drew Brees era, edging out the ballhawking unit that hoisted the Lombardi Trophy after the 2009 season.
6) Chris Jones, defensive lineman, Kansas City Chiefs
Jones has generated a sack in 10 consecutive games, the longest streak within a season since the stat became official in 1982. He and outside linebacker Dee Ford (11.5 sacks) are rivaling Denver's Von Miller and Bradley Chubb as the most productive pass-rushing tandem in the league. Far from a one-trick pony, Jones is fourth in tackles for loss (17), seventh in QB hits (26) and third among defensive linemen with five passes defensed.
7) Bobby Wagner, linebacker, Seattle Seahawks
Wagner doesn't miss tackles -- literally. Pro Football Focus credits him with zero missed tackles this season. It's an incredible feat, considering Kuechly as well as hotshot rookies Darius Leonard and Leighton Vander Esch have missed nine apiece. That thumper's skill set would seem to be at odds with the modern demands of the position, but Wagner is the rare tackling machine who also excels in coverage, earning PFF's highest grade among linebackers. Pete Carroll is right: Wagner is on a Hall of Fame trajectory.
8) Von Miller, outside linebacker, Denver Broncos
Speaking of future Hall of Famers, the Super Bowl 50 MVP is the defining edge rusher of his era. The master of the strip-sack has forced four fumbles to go with 18 combined sacks + stuffs. While Case Keenum's offense has disappointed this year, Miller and bookend rookie Bradley Chubb have led a reinvigorated defense that ranks fourth in Football Outsiders' metrics.
9) DeMarcus Lawrence, defensive end, Dallas Cowboys
Lawrence's raw sack production is down from last season, but he's still making a living behind the line of scrimmage with 9.5 stuffs and 11 QB hits to go with a flurry of hurries. Although he's tied for sixth with 23.0 sacks since the start of the 2017 season, his impact in the ground game isn't far behind. As much well-deserved hype as Vander Esch has received, Lawrence is the most disruptive force on Dallas' unexpectedly superb defense.
10) Darius Leonard, linebacker, Indianapolis Colts
My choice for NFL Defensive Rookie of the Year is perhaps the most egregious of this year's Pro Bowl snubs. Leonard doesn't just pass the eye test; he's also generating numbers unseen by the greatest inside linebackers of this century. He's averaging more tackles per game than Kuechly and Patrick Willis managed en route to Defensive Rookie of the Year honors. His seven sacks are more than Kuechly, Wagner, Willis or Ray Lewis ever posted in a season. He's also thrown in four forced fumbles and sterling pass defense for good measure.
Before Leonard arrived on the scene, the Colts were cupcakes. They have held their opponents to 10 points or fewer five times this season, a feat they had accomplished just six times in the past four seasons combined. This defense is allowing a minuscule 15.0 points per game since Week 7, the lowest number in the league over that span.
HONORABLE MENTION:Danielle Hunter, defensive end, Minnesota Vikings; Myles Garrett, defensive end, Cleveland Browns; Dee Ford, outside linebacker, Kansas City Chiefs; Akiem Hicks, defensive lineman, Chicago Bears; Fletcher Cox, defensive lineman, Philadelphia Eagles; Calais Campbell, defensive lineman, Jacksonville Jaguars; Chandler Jones, defensive end, Arizona Cardinals; Frank Clark, defensive end, Seattle Seahawks; Jamal Adams, safety, New York Jets; Eddie Jackson, safety, Chicago Bears.