A typical argument about defense generally leads one or two ways:

Total Points per game

Total Yards per game

But both are rather poor indicators of overall defense.  A team can easily lower both by running a very slow pace to the game, thus limiting the opponents opportunity to increase both, but also their own opportunities.

A better defensive stat is yards per play. And it generally plays itself out by the end of the season in the team rankings.  (As a point of reference, sub 4.0 yards per play (ypp) is generally at or near the top and sub 4.5 ypp will put a team around 10th or so in the country.

In 2009:

Texas 3.8
TCU 3.9
Nebraska 4.0
Alabama 4.1
Ohio State 4.1

Oregon 4.6 (tied for 11th)

Whereas for the points allowed argument:

Nebraska 10.4

Alabama 11.7

Texas (now in 12th place) 16.7

And at 50th...Oregon at 23.8 points allowed.

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So what, right? Who cares. 

But from 2008 to 2009 the Oregon Ducks went from allowing 4.9 ypp to 4.6 ypp.  Which put them at 11th in the team ranking in 2009 vs. 28th in 2008.

And 2009 was different from previous years as well:

(2007) 5.1 yards per play

(2006) 5.1 yards per play 

(2005) 5.0 yards per play 

So why was 2009 a successful season for the Ducks?  Better offense? After all 2008 was a disaster at QB for part of the year for UO (Chris Harper).  But the Ducks were still 7th in the nation with 485 ypg, 41.9 ppg and 6.6 ypp.

But in 2009 the Ducks only scored 36.1 ppg, 412ypg, and 6.1 ypp (slackers). 

It was the defensive improvement the keyed the Duck's run to the Rose Bowl.  And in my opinion Jerry Azzinaro was key to that improvement.  What else changed?  You could argue that previous teams had more talent, in 2008 the team had future draft picks Chung, Byrd, and WT3 in the secondary as well as Sir Nicholas Reed.

But I think that Azzinaro brought new schemes and an intensity that previous Duck defenses lacked.  The defense seems more confident and less apt to totally break down (Stanford being the outlier).  

So keep improving that defense and the wins will continue to pile up.