After spending time focusing on the USC offense in recent posts it is only fair to spend some time looking at the Trojan defense. If you have not done so already I suggest reading the links to the articles written by Pete Carroll on his defensive philosophy. The posts are located inside the March entries on this site.

Let’s start by taking a look at the overall USC defensive trends the past few years. There are a couple of key statistics to look at in review. For starters let’s break down the Trojan performance by total defense, run defense, pass defense, and scoring defense.

Total Defense Trend Chart 1998-2006

Pass Defense Trend Chart 1998-2006

As you can see the overall numbers are fairly stable during the Pete Carroll era but they do bounce around in any given year or category. In hindsight the 2002, 2003, and 2004 defenses excelled particularly in run defense. (Note: Keep in mind however that unlike the NFL college stats take sack yardage off of the run totals). None the less the average yards per run allowed in all of those seasons was still quite impressive. A stout run defense helps to put the opponents offense eventually into 2^nd or 3^rd and long situations and USC can then gamble taking more aggressive shots against the passing game.

I was curious to find out what aspects of USC’s defense have varied the most in the past couple of years. The answer was fairly easy to find. For the past two years the team has been on a downward trend in terms of sacks, tackles for losses, and turnovers. Despite the teams relatively strong performance in 2006 it still has a long way to go to match the levels of the 2002, 2003, or 2004 units. For starters here is the recent trend in sacks and tackles for losses (TFL’s).

The reasons for the decline in the above categories in my opinion are probably two fold and I can’t separate out the effects. First is the loss of key players such as Keneche Udeze, Shaun Cody, Mike Patterson, and Lofa Tatupu for example. Udeze had 16.5 sacks in 2003, Cody and Patterson combined for 16 in 2004, and MLB Lofa Tatupu also had 6 in 2004. The current defensive front four in the past two seasons has not matched this level. The sack leader in 2005 was Lawrence Jackson with 10. In 2006 the leader was SLB Dallas Sartz with 7 followed by DE Brian Cushing and NT Sedrick Ellis with 4.5 each.

To some extent the past two years however I also suspect that the opposition has also made some adjustments which are making it harder to generate sacks. The last two years it seems that the opposition is spreading the field more, putting the QB in shotgun formation, and throwing shorter passes to avoid the pressure. For a snap shot look at this possibility I charted in detail the second half of the game against Washington with Isaiah Stanback at QB for time study. He operated out of the shotgun on 20 of 25 snaps in the second half alone.

Stanback also remarkably released the ball within 2.33 seconds from the snap on the throws I took a look at and only threw them about 7 yards down field. As a result USC generated some pressure but it resulted in zero sacks for that game. I suspect this is probably true for other teams and is a trend that might continue in the future. It is at least something that I will be watching more closely in 2007 for comparison. This may simply represent a fundamental shift in the way some teams are going to attack USC in the future. Here is a snap shot of the data:

The defensive statistic that is probably most important to consider however is that of turnovers. USC’s performance in this regard has been stellar since Pete Carroll arrived. In 2000 the Trojans were next to last in the country in defensive takeaways. Since 2001 the team has been at the top of the charts almost every year. Oddly the exception to this trend is the 2006 season. This is the one area where that unit did not quite perform up to the standard of the previous years.

Another way of looking at the turnover deficit more clearly is to express it in total amount instead of turnover margin advantage. The figure for the total difference and trend is as follows when broken up into fumbles and interceptions.

Pete Carroll likes to comment that his philosophy is “all about the ball”. This means keeping it on offense until they score and taking it away from the opposition via turnovers on defense. A strong case can be made that what ailed points scoring in 2006 was in reality the defense and not so much the offense. USC scored 22 points last season on offense when forced to start on their own side of the field. This was the same level as 2003-2004 for comparison. However in 2006 the unit did not score as many points due to a shortage of opportunities starting inside the opponents 40 yard line. The reason for the decline in short field possessions? Turnovers. As the trend chart above shows USC forced nearly 20 fewer turnovers in 2006 than in 2003 for example. The average field position after a turnover for USC is the opponents 40 yard line. This drop off in turnovers directly correlates to the reduction in short field opportunities last season for the offense.

So what is the effect of this turnover deficit? Well the best we can do is extrapolate using some averages. USC scores about 70% of the time it enters the area inside the opponents 40 yard line. 75% of the time it is a touchdown and 25% of the time it is a field goal. So the reduction in 20 short field opportunities is the following. The 20 missing short field drives means 14 fewer scores in 2006 (e.g. 20 x .7 = 14). The results is as many as 84 fewer total points as mathematically (14*.75*7)+(14*.25*3) = 84. The effect of 84 fewer points converted to a per game basis is 84/13 = 6.5 points per game. Tack on 6.5 points per game to the 30.5 per game last season and suddenly you have 37 points per game or roughly just the Trojans average since 2001. Keep in mind the game was also about 10% shorter in 2006 as well due to changes in clock management rules by the NCAA. However I will ignore that factor for now although it is probably worth another 2-3 points in terms of effect. While it is true that Norm Chow for example was indeed a good play caller when he was offensive coordinator it is also important to note in hindsight that the USC defense generated far better field position for him to be aggressive with as well.