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Wednesday, April 30, 2008

2007 Defensive Line Performance

I hate to dwell too much on the 2007 season, but I have the data and feel I might as well not ignore it. Today, I give you my assessment of the play of the defensive line using a multitude of statistics only available via a closer look at play-by-play data from the previous season.

First off, let's start with what I said about the defensive line in my preseason preview of Nebraska:
"Defensively Nebraska must replace its entire defensive line from a year ago. That includes a pair of defensive ends in Adam "I must break you" Carriker and Jay Moore who were drafted in the first and fourth rounds of the NFL Draft. Barry Turner is being looked upon to take center stage in 2007 at one DE position. He's showed flashes of brilliance during the past two seasons, but must prove he can line up on every down. Turner unfortunately missed valuable practice time in the spring following shoulder surgery. Ndamukong Suh will anchor the line at one of the tackle spots and might actually be the best player on the defense. Finding someone to line up next to him will be a major task during fall camp. The wildcard might be Ty Steinkuhler who can play inside or out and has displayed an impressive motor in a reserve role. Ultimately, the group vying to replace the departures along the front four is heavy on potential, but light on experience. The bottom line is that a team rarely gets better by losing players like Carriker and Moore, along with defensive tackles Ola Dagunduro and Barry Cryer."
Well, I was certainly right about the drop in production and unfortunately Suh and Turner failed to live up to their billing in 2007. In Turner's case the blame might fall with the large amount of weight he gained heading into the season. With Suh, it might be a toss-up between a poor scheme that pulled him away from his strengths and a tendency to take plays off or at least fail to bring it on each and every down.

Now let's take a look at the actual numbers. For my analysis, I went a step beyond what you'll generally find in boxscores. I have included a set of statistics utilized by the guys at Football Outsiders in their work with the NFL. They employ a couple of interesting variables to examine the play of defensive players.

The first two are explained here:

Plays: Defined as the total defensive plays made, including tackles, pass deflections, interceptions, fumbles forced and fumble recoveries. These numbers come from official play-by-play reports and DOES NOT include special teams tackles or statistics.

TmPct: Refers to the percentage of team plays involving this defender. The sum of the percentages of team plays for all defenders on a given team will exceed 100%, primarily due to shared tackles. And here is a chart indicating the performance of Nebraska's defensive line on these two statistics. This is the type of analysis that can only be found at DXP.

Defensive Plays

Player TacklesPasses Def.INTsFFFR Plays TmPct
Zach Potter451111 495.44
N. Suh332001 36 4.00
Barry Turner292000 31 3.44
Kevin Dixon190100 202.22
Shukree Barfield150000 151.67
Ty Steinkuhler130010 141.56
Pierre Allen111000 121.33
Andy Poulosky70000 7.78
Clayton Sievers70000 7.78
Brandon Johnson30000 3.33
Ben Martin30000 3.33
Thomas Rice10000 1.11
Tony Sullivan10000 1.11

As these statistics illustrate, Zach Potter really separated himself as our most consistent defensive lineman in 2007. While he was nowhere near as productive as an Adam Carriker or a Jay Moore, he did make his share of plays and was underrated member of the Blackshirts.

The next three statistics take into account situational variables and determine a defensive player's ability to keep teams from moving the chains.

Stops: The total number of plays made by a defender that prevent a "success" by the offense. A successful play occurs when the offense obtains 45% of needed yards on first down, 60% on second down, 100% on third or fourth down. Therefore, a stop prevents one of these successes from occurring.

Defeats: The total number of plays made by a defender that stop the offense from gaining first down yardage on third or fourth down, stop the offense behind the line of scrimmage, or result in a fumble (regardless of which team recovers) or interception.

Stop Rate: Refers to the percentage of all of a defenders Plays that are Stops.

Stops and Defeats

Player StopsDefeatsStop Rate
Zach Potter281357%
N. Suh23864%
Barry Turner17455%
Kevin Dixon10450%
Ty Steinkuhler10371%
Shukree Barfield7247%
Pierre Allen7258%
Andy Poulosky4157%
Clayton Sievers2229%
Brandon Johnson2067%
Ben Martin2067%
Thomas Rice10100%
Tony Sullivan10100%

You'll notice that these numbers probably seem pretty low, but unfortunately I don't have comparison data at this point, so that is difficult to guage. Again, however, you see Zach Potter standing out. Suh also has some decent numbers which I think only highlight his potential. Overall, given our inability to get offenses off the field, you won't see big numbers in terms of stops and defeats.

The final area to examine are the defensive linemen's sack numbers from 2007.

Player Sacks
Barry Turner 3
Zach Potter 2.5
N. Suh1
Andy Poulosky 1

What should immediately jump out is the complete lack of sacks up front in 2007. 7.5 goddamn sacks from our front four? That's all we got? In 2006, Carriker and Moore combined for 13 sacks just by themselves. Another way of looking at the defensive line's performance is by examining the percentage of the team's total sacks that they accounted for. In 2007, Nebraska totaled just 13 sacks (yikes!), of which the defensive line accounted for 7.5. In other words, the defensive line combined for 57.7% of the total sacks in 2007. That's way down from the 24 out of the 31 total sacks (77.4%) the D-Line accounted for in 2006.

2008 Outlook

The good news is that Nebraska returns almost everyone up front from 2007. But given their numbers from a year ago and the influx of a new coaching staff it is difficult to guage how they might perform. I think Zach Potter found himself last season and should continue his consistent play. Barry Turner has slimmed down and hopefully will regain his speed. If that happens, watch for Pelini to let him loose on the edge. Inside, Suh and Steinkuhler return as do Kevin Dixon and Shukree Barfield. I think Suh could be the one guy who benefits most from the arrival of the new coaching staff. By all accounts the guy has gobs of talent, but he's quickly running out of opportunities to showcase that at the college level. He could be one of those guys that underachieves in college, but explodes in the NFL simply because he will only be called on to deliver on 20 plays a game, with the depth NFL squads possess up front. Rotations like that mean a ton when you're carrying 300+ pounds.

Speaking of depth, Nebraska still lacks it up front. At DT, Dixon came on strong in Big 12 play and has drawn praise this spring as well. In addition, guys like Shukree Barfield and redshirt freshman Terrence Moore likely benefitted from Suh's absence this spring as he recovered from surgery. The somewhat strange departure of Seth Jenson, however, hurts the development of depth down the road and makes DT recruiting all the more important in 2009. Overall, the defensive line has nowhere to go but up in 2008 and I expect to see a new brand of intensity and pressure up front.