-- There is no argument over which defense is the best in college football this season. Zero. Zilch. None.
The Alabama Crimson Tide lead the country in points per game, yards per game, yards per play, Total QBR and, well, just about every other major defensive category this season.
But the question still remains: Is this the best Bama defense Nick Saban has ever coached? Entering this season, most would have agreed that Alabama's top defense under Saban was the 2011 national championship-winning squad. That team allowed only nine offensive touchdowns and has been widely regarded as one of the best defenses in college football history.
So how do the two compare?
Based on traditional statistics, Alabama's 2016 defense does not compare to its 2011 team. The 2011 unit -- led by top-35 NFL draft picks Dont'a Hightower, Courtney Upshaw, Mark Barron and Dre Kirkpatrick -- allowed the fewest points per game and yards per game of any defense in the past 25 seasons. And their season totals blow away the marks set by this year's Alabama squad.
Notable Alabama Defenses Under Nick Saban
(best in a season since 1988 Auburn allowed 7.2 PPG)
2016 11.4 PPG
Yards per game
2011: 183.6 YPG
(fewest allowed in a season since 1986 Oklahoma allowed 169.6 YPG)
2016: 244.0 YPG
Yards per play
2011: 3.3 YPP
2016: 3.9 YPP
But sometimes base-level stats can be misleading. For example, the yardage totals do not account for the significant impact of turnovers (and subsequent defensive touchdowns). They also do not account for the strength of offenses faced or the context of when the yards came.
Digging deeper into advanced stats -- which account for all of those factors and more -- tells a different story. The 2016 Alabama defense is the top unit of the past decade by defensive efficiency -- and it's not even close!
ESPN's defensive efficiency ratings capture a defense's per-play contribution to the team's scoring margin, adjusting for opposing offenses faced. These ratings are built off the framework of expected points added (EPA), which accounts for the context (down, distance, yard line, etc.) of every play by measuring the change in a team's scoring potential from one play to the next. If a defense stops a team on third down (no matter how many yards are gained), forces a turnover or stymies an offense in the red zone, it generally results in negative EPA for the offense and positive EPA for the defense.
While the explanation of the statistic may be complex, the rationale behind it is intuitive. Good defensive plays result in high defensive EPA, and over the course of the season, the best defensive teams almost always end up leading the country in this category. Defensive efficiency takes this statistic a step further and adjusts for pace, the strength of opposing units faced, and blowout situations. It is expressed on a 0-to-100 scale (50 is average) for easier understanding.
Alabama leads the country in defensive efficiency by nearly 10 points this season, and is on pace to end the season with by far the top mark of any team in the past decade.
Highest single-season defensive efficiency, past 10 seasons
1. 2016 Alabama: 98.2 (on a 0-to-100 scale)
2. 2011 Alabama: 94.5
3. 2014 Clemson: 92.5
4. 2015 Alabama: 91.6
5. 2012 Alabama: 91.2
Why is Alabama's 2016 squad rated so much higher than its vaunted 2011 unit? Below are three reasons that are likely lost in the traditional, base-level numbers.
Alabama's 2011 defense bulldozed teams with its size and power -- it simply did not allow opponents to move the ball. The 2016 version of the Crimson Tide D is less physically imposing but equally scary because of its ability to change the game with one swift play.
Alabama's defenders relish the opportunity to force a turnover and take it to the house. The Crimson Tide have 11 defensive touchdowns this season by eight (yes, eight) different players. Nine of the 11 touchdowns came against AP-ranked opponents, and most came when the game was still in question.
Though Alabama is tied for eighth nationally in turnovers forced this season, the impact of those turnovers sets them apart from other defensive units historically. Alabama has added an FBS-high 121 expected points to its net scoring margin as a result of its turnovers, including 79 such points on its 11 defensive touchdowns (this takes into account that the offense may have been in positive or negative position when allowing a defensive score). No defense since 2005 has had such a large impact because of defensive scores.
Strength of offenses faced
Before adjusting for opposing offenses faced, the 2011 and 2016 Alabama defenses have the best defensive EPA marks in the past decade by a wide margin. Both units added about 19 points per game to their team's net scoring margins and were equally impactful over the course of the season.
Once adjusting for the opponents faced, however, the 2016 unit is the clear top defense during that time. While many will question Alabama's competition this season, the Tide still went up against nine offenses ranked in the top 35 in offensive efficiency and five starting quarterbacks in the top 25 in Total QBR ( Jake Browning, Chad Kelly, Joshua Dobbs, Nick Fitzgerald and Mike White). The '16 unit also faced 10 players who rushed for at least 1,000 yards this season and didn't allow one to break the 50-yard mark. By comparison, the 2011 defense faced three teams (Arkansas, LSU twice) in the top 35 in offensive efficiency, one starting quarterback (Tyler Wilson) in the top 25 in Total QBR, and five 1,000-yard rushers.
Sure, Alabama had the luxury of facing the USC Trojans before they hit their stride, but it also took on Ole Miss with Kelly and LSU with Leonard Fournette. It's fair to question the strength of the SEC overall, but there's no denying that Washington, USC and even Western Kentucky have playmakers who were shut down by the Crimson Tide.
Ability to get after opposing QBs
Before the SEC title game, Florida coach Jim McElwain, who was the offensive coordinator at Alabama in 2011, said Alabama's 2016 defense "might actually even have more overall team speed" than the heralded 2011 unit.
Nowhere is that more apparent than along the defensive line, where Alabama has been ferocious in getting after the quarterback. The Crimson Tide rank second nationally in both sacks (50) and pressure percentage (42 percent). They have 20 more sacks and nearly twice the pressure rate of the 2011 squad.
Accounting for the context of their sacks and overall impact, no defense in the past 10 seasons has added more expected points on sacks than this 2016 Alabama team.
So the Crimson Tide appear to have the edge in the all-encompassing, opponent-adjusted advanced statistics, but they still have one more test before they can be crowned the greatest defense under Saban. If Alabama can solve the riddle of QB Deshaun Watson and again beat Clemson for the national title, this defense should be considered not only the best under Saban but also the greatest in recent memory.