Alabama By the Numbers: Interceptions

TUSCALOOSA, AL - OCTOBER 22: Nico Johnson #35 of the Alabama Crimson Tide breaks forces an interception as he breaks up an pass intended for Mychal Rivera #81 of the Tennessee Volunteers at Bryant-Denny Stadium on October 22, 2011 in Tuscaloosa, Alabama. (Photo by Kevin C. Cox/Getty Images)

In 2009 and 2010, Alabama's defense ranked in the top five squads in the nation for interceptions. A sky high turnover margin for those years was fueled by the secondary's propensity for picks. Heading into 2011, the experience among the defensive backs was expected to be one of the strengths of the Crimson Tide's team. Yet, at first glance, that plan seems to have gone awry.

Total Interceptions 2007-2011

Source: CFB Stats

That's right, Alabama had fewer interceptions in 2011 than in any year under Nick Saban. The Crimson Tide's 13 picks last season were tied for 43rd in the nation. The total marked a more than 45 percent dip from the tally collected by the 2009 BCS National Championship squad who were outdone that year by just one other team -- Texas, ironically enough.

At the same time Bama's quarterback corps tossed a total of eight interceptions in 2011, a bit of an uptick after two consecutive years with just five picks. With a new quarterback taking over the offense we were expecting an increase but it still stayed far under the totals the reasonably efficient John Parker Wilson tallied.

At first glance, this would seem pretty bad. Yet it might not be as simple as the overall numbers suggest. Here's a look at the number of pass attempts per interception for each of the past five seasons.

Pass Attempts per Interception 2007-2011

Source: RollTide.com

Once again, it's not too hard to pick out Greg McElroy's skill at avoiding interceptions. In two years under center he threw just nine picks. But, as we saw yesterday, his ten fumbles in 2009 and 2010 were significantly more than any other Crimson Tide player and led to five turnovers. AJ McCarron threw just five picks last season and fumbled only twice although both were turnovers (and one a touchdown).

So, basically, McCarron matched McElroy's average turnovers but fumbled the ball less than half as much. Yet this might not be a completely fair comparison as we'll see in a moment. More to the point Alabama's putting a premium on mistake-free QB play may give critics fodder to claim Alabama QBs are "just" game managers, but if that's the biggest downside we can live with it.

As for the Tide's opponents, the 25.1 pass attempts per interception last season was the second-highest mark in the Nick Saban era. Not a huge surprise given the scarcity of Crimson Tide picks in 2011 compared to the rest of the last half decade. Again, this isn't necessarily the bad news it seems to be since, as you are certainly aware, Alabama boasted the No. 1 pass defense and the No. 1 pass efficiency defense last season.


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Now let's take a look at a few of Alabama's pass defensive statistics over the past five years broken down to their per game average.

Alabama Pass Defense 2007-2011

Source: RollTide.com

Alabama had more interceptions, passes defended and quarterback hurries per game in 2009 but finished the season at No. 2 in pass efficiency defense and No. 10 in pass defense. The number of sacks per game were about the same for both Tide title teams. So even though the 2009 National Championship defense had better numbers, it ranked somewhat lower nationally.

So let's switch to the other side of the ball and look at the per-game pass defensive statistics for Alabama's opponents over the last half-decade:

Opponent Pass Defense 2007-2011

Source: RollTide.com

Now things make a bit more sense. The ongoing downward trend of passes defended by Tide opponents speaks somewhat to the accuracy of the Bama passers but it also probably has a lot to do with teams stacking the box to stop the likes of Mark Ingram, Trent Richardson and Eddie Lacy.

Even more impressive is the work of the offensive line protecting AJ McCarron last season. With sacks and quarterback hurries plummeting to a five-year low, the first-year starter was given the best possible chance to find his footing. Obviously, the offensive scheme probably had a lot to do with that as well. But a surfeit of short, high-percentage passes isn't going to totally account for that much of a dramatic change.

We also get a bit of an idea why Greg McElroy seemed to struggle more in his last season than he did in 2009. Interestingly McElroy had a better completion percentage (70.9%) in 2010 than he did in 2009 (60.9%).

So what can we surmise from all this? Did Alabama's pass defense regress last season or is something else happening here. It's actually the opposite. In January we produced a Alabama By the Numbers post that explained, in some detail, exactly how dominant the 2011 BCS National Champion defense was. Rather than go back through all that information we'll look at first downs per game (a shorthand measure of Alabama's ability to keep drives alive and deny the same of the opposition):

First Downs per Game 2007-2011

Source: RollTide.com

First off, we get a good look at how the 2011 Tide offense kept chugging along quite nicely. The 21.5 first downs per game was comparable with other Alabama offenses under Coach Saban and the squad's third down conversion rate of 47% -- which was above his team target (45%).

On the other hand, Alabama's defense simply stopped opposing offenses in their tracks last season. The 10.8 first downs allowed per game was the fewest in Alabama football history since 1962 (9.91). You also have to go back that far to find a Crimson Tide defense that permitted fewer yards per game than the 2011 team. The third down conversion rate for Alabama's opponents -- 24% -- was the lowest in the five years Coach Saban has been at the Capstone (his target for the team is 30%).

Another way to look at this is by the number of plays Alabama defended against last year (as suggested by zeke2029 on Tuesday). The 720 plays the defense were on the field for was the fewest in the nation and 15% less than what the 2009 squad faced in their successful run at the crystal football. Of course the 2011 Crimson Tide team played one game less but even accounting for that, they were still significantly more efficient.

Plays Defended Against per Game 2007-2011

Source: CFB Stats

So it seems plausible that the dearth of gaudy numbers on the part of Alabama's pass defense had a lot to do with the overall proficiency of the defensive unit. The inability of opposing offenses to stay on the field limited the opportunities the Tide defenders had to maul them. In this respect, they were a "victim" of their own success.

Total Interceptions Made
Alabama Opponent
2011 13 8
2010 22 5
2009 24 5
2008 15 9
2007 19 12

Attempts per Interception
Alabama Opponent
2011 44.6 25.7
2010 72.4 16.7
2009 69.2 18.7
2008 37.1 31.1
2007 39.3 22.5

Alabama Pass Defense Stats per Game
Pass Defl QB Hurry Sacks
2011 5.3 3.1 2.3
2010 6.1 4 2.1
2009 7 5.6 2.3
2008 5.1 4.2 1.9
2007 3.3 3.4 1.9

Opponent Pass Defense Stats per Game
Pass Defl QB Hurry Sacks
2011 2.8 1.2 1.3
2010 3.1 3.1 2.5
2009 3.1 2.5 1.4
2008 3.4 3.1 1.8
2007 3.4 3.5 1.9

First Downs per Game
Alabama Opponent
2011 21.5 10
2010 22.1 15.2
2009 20.6 13.4
2008 18.8 14.1
2007 22.8 18.1

Statistical note: For much of these more in depth analyses we are relying on the numbers provided by Alabama Athletics on RollTide.com. We have used the NCAA numbers available on CFB Stats to compare Alabama's performance across college football but those are not as detailed as the UA information. In addition, there are slight discrepancies between the two sets of data.

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