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2015 Alabama Defense Rivals 2014 Clemson Defense In Performance

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Robert Duyos-USA TODAY Sports

We've heard a lot of talk about how good Alabama's defense is. It is certainly the best in the country this season, both by the eye test and by the advanced stats. But even though they are the best, how can we determine just how good they are?

Luckily Clemson fans have a great reference point, the 2014 Clemson defense. Last year Clemson had a 8 DL that would start on 95% of teams across the country. We had a solid LB corp with some freak athletes and great performances. We also  had a very talented backfield that was able to capitalize on the DL's excellent play.

But we all know the eye test can certainly be deceiving, so what do the stats say. Below are some of the main statistics from Football Outsiders S&P+ and FEI for a comparison.

Category Clemson 2014 Alabama 2015
S&P Defense 12.2 6.8
Rushing S&P+ 146.7 157.3
Passing S&P+ 158.2 155.7
Standard Down S&P+ 141.8 153
Passing Down S&P+ 167.7 154.1
Success Rate+ 147.2 162.1
IsoPPP 161 151.5

For reference, a glossary of these terms can be found here.

The big thing that stands out here is how both defenses are talented, but there are differences. Clemson was a little better at stopping the Pass while Alabama excels against the rush Clemson was extremely strong on passing downs and IsoPPP while Alabama is dominant at Success Rate, a product of their strong rushing defense. The one big shock comes from the overall S&P Defense ranking, lower is better. This stark difference likely happens because Alabama is so successful in their success rate. S&P is a play based metric and can favor defenses that are much more about stopping each play than one that may let drives go on longer.

The other group of stats to look at is FEI. Also found on Football Outsiders, FEI is a drive based ranking system more concerned with the outcome of a drive rather than individual plays.

Category Clemson 2014 Alabama 2015
Defensive FEI 1.18 1.07
1st Down Rate .545 .576
Available Yards % .254 .270
Explosive Drive Rate .097 .079
Methodical Drive Rate .052 .086
Value Drive Rate .182 .174

Here because the numbers are all rates and percents a lower number is better except for the overall total, for a full explanation go here.

In FEI, Clemson was ranked much better than Alabama overall, though the details show a bit of a split. Clemson has a good edge in 1st down rate, likely due to the confidence in the DL to attack the QB and RB, as well as a big difference in available yards  and methodical drive rates. Alabama has the advantage in explosive drives and value drives.

This matches up with what we've seen. Alabama this year is hard to score on with a big play. But teams that have success against them are able to get those big plays. Field position is also critical against Alabama, they do well at preventing value drives, those that start in your own half and go past the opposing 30, and combined with the lack of explosive drives means scoring is difficult. But teams scored against Clemson last year and you can score on Alabama this year.

From FEI a key is going to be 1st down. If Clemson can move the ball on first down it is going to help. Even if it is only 3-4 yards, it moves pressure to the defense and opens up options for the Clemson offense.

Finally, for the less advanced stat inclined of you, let's look at some traditional measures of defense.

Category Clemson 2014 Alabama 2015
Yards per Game 260.8 256.8
Rushing YPG 100.46 70.8
Passing YPG 178.2 186
Yards per Play 4.03 4.09
Scoring Defense 16.7 13.4
Sacks per game 3.46 3.57
Opponent 3rd Down Conv. 27.41 27.7
Turnovers 24 26

As you can see, once again everything is pretty close. Both defenses have some advantages over the other. Clemson did a better job on yards per play and in the pass game while Alabama had a better scoring defense and rushing defense.

Now one caveat here, it can be hard to compare across seasons because the offenses these teams face can be very different in ability. Yes, the advanced stats are opponent adjusted for the season, but it is possible offenses in 2014 were better than 2015 or vice versa. But even with this note it is obviously that Alabama's defense is going to be difficult to crack for Clemson. Unless we suit up Cole Stoudt in some Crimson and White....