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Knock down quarterback good.

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Boiled down to its basics, playing offense successfully in the sport of football is pretty simple:

• Gain 10 yards in 3 tries.
• Repeat until you reach the the end zone.

(We'll skip the "does punting really make sense?" debate for now.)  At the hypothetical extreme, a team that could gain exactly 3.5 yards on every play could achieve that goal.  Alternately, two rushing plays of 5 yards each or a single pass completion in three attempts for 10 yards does the trick.

The goal of any football defense, then, has to be to disrupt the opposing offense's rhythm, with the goal of creating a situation where picking up 3-5 yards per play isn't enough to keep a drive going.

Looking at the statistics available to us, there are four quantitative indicators of a defense's ability to disrupt the opposing offense.  In ascending order of disruptiveness:

• Quarterback hurries: Increasing the odds the offense will throw an incomplete pass and lose an opportunity to gain yardage
• Tackles for loss: Increasing the yardage the offense has to gain to achieve a first down by sacking the quarterback or stopping a running play for a loss
• Forced fumbles: Creating the opportunity to recover a fumble and end the opponent's offensive possession
  
• Interceptions: Definitively ending the opponent's offensive possession

(If specific stats on penalties by the opposing offense--holding, etc.--were readily available, I'd include those, as well.  Also, I'm defining "forced fumble" liberally, counting any fumble by the offense, even if it's not directly attributable to a defensive player.)

With the goal of creating a nifty new statistic, we can start by summing these four numbers.  There's some double counting involved (a sack can result in a forced fumble, a quarterback hurry can result in an interception), but those instances tend to place more weight on turnover-inducing plays, which is fine.  The summed number is then divided by the number of plays run by the opposing offense (tempo-free!) to arrive at a number we'll call Disruption Percentage.

Here are the Disruption Percentage numbers for MSU's first seven games this season:

File this table under "Promising Trends."  After making disruptive plays on only about one-tenth of plays by the opposing offense in the first three games vs. FBS opponents, the MSU defense boosted the percentage to 25.0% for two consecutive games and then put up a decent percentage last week--in light of the fact that Northwestern ran so many short pass routes, which presumably makes it harder to disrupt the play.

Some of the trend has to be chalked up to the order in which our opponents were scheduled.  Notre Dame has the most efficient offense in the nation according to Football Outsiders, and Central ranks in the top 30. Illinois, on the other hand, ranks among the 20 least efficient offenses in the country.  But Wisconsin, Michigan, and Northwestern, are all in the 35-50 range--so the improved numbers against the Wolverines and Wildcats are definitely an encouraging sign.

(Sidenote, in case you didn't click through to the FO page: MSU currently ranks #7 nationally in offensive efficiency, adjusted for strength of opponents, and #42 in defensive efficiency.  Iowa is #16 on offense and, SHUDDER, #1 on defense.)

MSU only had to replace 4 defensive starters from last season, but two of those starters were defensive linemen who had combined for 15.0 TFLs last year (Brandon Long and Justin Kershaw) and another was Otis "Turnovers Are My Middle Name" Wiley.  So it may have taken some time this season for the defense to get into a disruptive groove (the emergence of Jerel Worthy has certainly helped; see below).  Let's hope the numbers are telling a real story here and the 2009 version of the defense--now having that base 4-3 defense down cold--will continue to consistently create disruptions for opposing offenses, starting this Saturday vs. Mr. Stanzi (8 INTs, 133 negative rushing yards) and Co.

Appendix: 2009 MSU Individual Defensive Disruptive Play Leader Board