Alright, folks. Spring practice is officially over, which mean we are now in the unforgiving grip of the wasteland known as "the offseason". Accordingly, we'll be revisiting the "A Cut Above" series and picking up where we last left off. Today, we will be looking at a bit of statistical analysis of the Tide's defensive performance under Saban, and trying to see what relevant insights we may glean from the numbers.
As before, all stats are taken from cfbstats.com, and just like last time, we'll start off by looking at the all of the raw numbers that we will be working with:
Obviously, the most important metric when evaluating a defense is points allowed. It's the cleanest and simplest metric there is, and ultimately, it's the only one that counts on the scoreboard. It shouldn't surprise anyone that's been watching college football the last half-decade, but the numbers bear out that the Tide's defense has been pretty good.
Unlike the offensive graphs, the improvement of the scoring defense was less incremental and more of a precipitous drop. After only two years at Bama, Saban had slashed the point per game (PPG) allowed roughly in half. In doing so, he very nearly maxed out how well a team can reasonably hope to perform statistically in the modern era. The national rankings reflect this massive shift as the Tide had the following national rankings in '07 thru '12: 27th, 7th, 2nd, 3rd (tie), 1st, and 1st, respectively.
Unlike the offensive graphs, there is a great deal more variance in year-to-year performance. Rather than the consistent improvement, we see more ups and downs that have a general positive trend.
Last year's defense saw a bit of regression from the previous year's absurd mark, but the '12 squad was pretty fantastic in its own right. The nation-leading 10.9 PPG mark set by Bama last year was only bested by three teams in the last six years. One of those three was the '11 Bama team. This means that in the last two seasons, Bama has fielded two of the best four scoring defenses of the last six years.
There are a few immutable truths in this life. Light travels faster than sound. Change is inevitable. And you don't run against a Saban-coached Bama team. Since 2007, Bama is giving up an average of 82.43 rushing yards per game. This includes the outlier of the '10 defense that gave up 110.15 rushing yards per game. Outside of that year (and obviously not counting '07), no Bama defense has given up more than 79.36 rushing yards per game. That's just filthy defense. And the craziest part is that the numbers aren't weighted down by beneficial outliers. To illustrate the Tide's consistency in this metric, the '11 defense (widely regarded as one of the best ever in college football) only held teams to two fewer rushing yards per game than the '08 team, and four fewer rushing yards per game than the '12 team.
Where the '11 defense really made it's hay was in pass defense. On a per game basis, the '11 defense was nearly fifty-five passing yards better than the next best Bama defense (111.46 in '11 to 166.00 in '09). That's taking a third off the passing YPG of the next best performance. Unreal. Incidentally, despite all of the hand-wringing over the "disappointing" performance of the '10 defense, that team's passing YPG were roughly equivalent to last years' numbers (176.23 in '10 to 173.64 in '12).
Obviously, the real disappointment of '10 was in rush defense. Some of this disappointment is due to high expectations. While the '10 team was not nearly as stout against the run as the two Bama teams on either side of it, its yards per game mark was still good for 10th in the country. If this is truly the absolute low-water mark of a Saban defense, then I recommend everyone mail a box of little debbie's to Tuscaloosa immediately.
How good is Bama against the run? You can count 2007's numbers, and the Tide still allows an average of less than three yards per carry. The best performers in this metric were the '11 and '12 teams, which both held opponents to 2.43 yards per carry.
Pass defense has a bit more variance, and helps to further a recurring theme of this piece - that the gulf between the "disappointing" 2010 defense and the "fantastic" 2012 defense is really more of a creek bed. On a per play level, the '12 defense only allowed 2.59 fewer pass yards than the '10 defense.
The value in this graph is derived from combining this information with the overall scoring defense numbers. For instance, the fact that the '12 and '10 teams allowed the same amount of TDs might cause alarm without considering that the '12 team played an extra game. The biggest takeaway from this data for me is how bad the '12 team was at preventing rushing TDs, when compared to the four years prior. While the '12 team only allowed .71 rushing TDs a game, this is substantially worse than the '08-'11 marks of .36, .36, .46, and .23, respectively.
This makes for some really odd conclusions. For instance, how do you reconcile the fact that the '11 and '12 teams allowed the exact same YPC, but the '12 team was three times more likely to allow a rushing TD? I suspect we'll get to that in just a bit.
Once again, we see that there has been a good deal of consistency by the defense since '08. These numbers aren't bad (most are good enough to be top 10 nationally), but only the '11 defense stands out as truly elite. We also see that, in yet another metric, the difference between the '10 team and the '12 team was effectively inches. The more metrics we look at, the stranger the 2012 defense seems. As I said at the beginning of this piece, that defense was the fourth best scoring defense of the past six years. And yet, it was one of Saban's worst in terms of rushing touchdowns allowed, third down defense, and as we'll look at next - red zone defense.
The biggest mislead in this data is the score percentage. Bama's defense kept this percentage relatively low in '12, and in fact was good enough to rank third in the country. But this is the mother of all red herrings, as when we look closer, and break the numbers down into TD% and FG%, we see that the '12 defense was the worst fielded by Saban, excluding the '07 season. In fact, the 55.17% TD% posted by the '12 defense ranked 42nd nationally. Forty. Second. Admittedly, Bama was working with little wiggle room, as it had the third fewest opponent trips into the red zone, but that isn't a dynamic that is new to the team, and I found it striking that we were that bad in this area.
In my mind, this particular metric goes a long way to defend the '10 defense, which at 32.26% posted the lowest red zone TD % of any Saban-coached Bama team. It also should serve as a wake up call for next year's defense. I really don't care what the metric is. There is no excuse for Bama to be ranked 42nd in anything at this point.
To try to explain how the '12 team was a better scoring defense than the '10 team despite being demonstratively worse in the red zone, we'll move on to our last metric take a look at the number of opponent red zone attempts per game.
As you can see, a trip into the red zone is in itself something to be celebrated when playing Bama. On average, a team can bank on two trips to the red zone. Anything more than that is a win for the opposing team. That being said, last year's team was actually a bit worse than the six-year average (2.05) and was not that far off the mark set in '10. We know that some portion of the scoring differential between '10 and '12 can be attributed to the increased number of trips allowed into the red zone, but the fact that the '10 defense was nearly half as likely to allow a red zone touchdown as the '12 defense, I think that this difference more or less cancels itself out. This means that the difference must be attributable to plays that occurred beyond the twenty - meaning that the '10 defense was susceptible to giving up longer scoring plays than the '12 defense. The '10 defense was not fundamentally unsound, however, or else they wouldn't be able to post such a ridiculously good red zone TD %.
So, in conclusion, I think the numbers pretty clearly demonstrate that, while the '10 defense was prone to occasional lapses resulting in longer scores, it really wasn't that far off the mark relative to the other Bama defenses of the last five years, particularly when compared to last year's national championship defense.
The next time we revisit the defensive statistics, we will be trying to analyze the trends discussed in this piece to try to make an informed estimate of how the '13 squad should perform statistically. Tune in next week, when we'll be analyzing turnovers in the Saban era.