Individual Defensive Numbers
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We've discussed it before, and it's worth bringing up again -- when it comes to evaluating defensive performance, standard stats are somewhat revealing, but not necessarily specifically informative. Middle or inside linebackers lead the NFL in tackles every year because ballcarriers flow to them, not because they're all over the place, making plays. Cornerbacks with high interception numbers could be doing that work against sub-average quarterbacks. One edge rusher with six sacks could be more valuable to his team than another edge rusher with twice the sacks, because the first guy is far better against the run.
Of course, the point of football is to win, not to accumulate positive individual numbers. And a big part of winning is making those plays when they really count more than the opponent does. Two of the principal philosophies we hold at Football Outsiders are that plays should be indicated as more valuable in specific conditions, and that plays should be given more value when they're made against a better team. That's where many of our stats come from -- the whole point of DVOA and DYAR is to adjust for opponent and give a performance rating against a baseline, so it's easier to tell what a team's really doing out there.
On defense, it's not just about tackles, it's also about where those tackles happen and what effect they have. We have two stats to reflect this:
Success Rate: The percentage of plays targeting a defensive player on which the offense did not have a successful play. This means not only incomplete passes and interceptions, but also short completions that do not meet the 45%/60%/100% baseline for success detailed in the description of DVOA.
Defeats: The total number of plays by a defensive player that prevent the offense from gaining first down yardage on third or fourth down, stop the offense behind the line of scrimmage, or result in a turnover. "Plays" refers to tackles, passes defensed, fumbles forced, or interceptions.
In short, Success Rate reflects gradations of defensive effectiveness, and Defeats indicate the ability to bring offensive drives to a quick close. Who had the best Success Rate and most Defeats at any defensive position in 2009?
Most Successes, Overall Defense
Justin Tuck, New York Giants, 55
Trent Cole, Philadelphia Eagles, 51
Aaron Schobel, Buffalo Bills, 50
Marques Douglas, New York Jets, 50
Andre Carter, Washington Redskins, 50
Most Defeats, Overall Defense
Aaron Schobel, Buffalo Bills, 30
Jared Allen, Minnesota Vikings, 27
Andre Carter, Washington Redskins, 26
Ray Edwards, Minnesota Vikings, 25
Trent Cole, Philadelphia Eagles, 23
Stats heavy in edge rushers, with the addition of Minnesota's dominant ends when we're talking about defeats. How about linebackers -- the guys who always lead the league in tackles? Who has the best Stop Rate, defined as plays by a defensive player that prevent a successful play by the offense, defined as 45% of needed yards on first down, 60% of needed yards on second down, and 100% of needed yards on third or fourth down?
Best Stop Rate, Linebackers
Anthony Spencer, Dallas Cowboys, 68 percent
Lawrence Timmons, Pittsburgh Steelers, 66 percent
Lance Briggs, Chicago Bears, 66 percent
Aaron Curry, Seattle Seahawks, 65 percent
Nick Barnett, Green Bay Packers, 64 percent
Which safeties had the most defeats? An interesting mix of old and new.
Adrian Wilson, Arizona Cardinals, 24
Louis Delmas, Detroit Lions, 21
Roman Harper, New Orleans Saints 20
Gibril Wilson, Miami Dolphins, 19
Brodney Pool, Cleveland Browns, 19
And finally, the same stat for cornerbacks:
Charles Woodson, Green Bay Packers, 29
Terrell Thomas, New York Giants, 24
Darrelle Revis, New York Jets, 22
Ronde Barber, Tampa Bay Buccaneers, 22
Brandon Flowers, Kansas City Chiefs, 21
We'll get more in depth with these numbers and what they mean during the offseason, but this is a good starting point when it comes to these numbers. Next week, we'll be using some of them in the Smarter Stats Super Bowl Preview.
By
Doug Farrar
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January 29, 2010; 12:00 AM ET
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