2011 Stats: 97 tackles, four forced fumbles, one interception, two sacks, 12 pass break-ups
Again, stop me if you've heard this already, but I think genuinely great defenders are genuinely great at all facets of the game.
And if that is the criteria for a list such as this, I think only linebackers really qualify. They have equal parts run and pass responsibility. Furthermore, they are often charged with being "the quarterback of the defense," calling out plays, schemes, blitzes, adjustments and/or coverages.
Under that specific set of guidelines, Patrick Willis earns the top spot for this specific list.
He was the anchor of a run defense that surrendered the fewest rushing yards (by far) in the NFL last season.
Despite missing three starts, he forced five turnovers all on his own and contributed an additional pair by recovering two fumbles.
And even though he doesn't post DeMarcus Ware-like numbers, Willis is still a very, very capable pass-rusher; besides, with Justin Smith, Ahmad Brooks and rookie Aldon Smith (28.5 combined sacks), defensive coordinator Vic Fangio doesn't really have to blitz his star inside 'backer.
That's especially true considering how productive he is in zone and man coverage. The 12 passes Willis batted down (again in a 13-game season) were more than excellent defensive backs like Tampa Bay's Aqib Talib, Denver's Champ Bailey and San Diego's All-Pro Eric Weddle.
If the fate of a game or a season rides on your defense making one stop of either a run or a pass, I'd want Willis on the field and in the middle of that unit, above any other player in today's game.