Steel Curtain Pt. II: Quantifying Pittsburgh's Defense Into Wins Above Average

Pittsburgh had a below-average offense in terms of points scored on the year. Yet they're 12-4.

Want to guess how good their defense must be?

They give up 11 points in their wins, 14 overall. In the past seven weeks, they've given up 12 points per game—which would only lower to only nine a game without a loss to the Titans in which they gave up 31 points.

They rank first across the board in total yards, passing yards, and points allowed per game, and second in rushing yards per game (at just over 80 per game). Even more unbelievable? Those 80 rushing yards per game come at the expense of a five-game stretch to end the year in which opponents averaged over 110 yards per game—the Steelers were giving up only 67 yards per game in their first 11 games.

You've heard the stat: The Steelers went the first 14 games without an opponent reaching 300 total yards.

How many wins did the Steelers' defense ultimately provide them, compared to if they were stuck with an average defense and below-average offense? Tennessee and Baltimore both came within 21 points allowed on the season; can we expect the Steelers' defense to still be atop the league?

The Pythagorean formula is used to project a team's record based on points scored and points allowed. We can use this to determine how many wins above average the Steelers' defense was this year, by finding how Pittsburgh's Pythagorean win total differs by changing out their stout defense to the league average (352.5 points scored/allowed on the year).

Say, for example, the Steelers were projected to win 11.4 games with their current points scored and allowed totals, but only 8.1 with a league average defense. In this case, the Pittsburgh defense would be worth 3.3 wins above average.

Here are the top and bottom five in the league.

Defensive Wins Above Average
Team	W	adj._W	diff
Pittsburgh Steelers	11.8	7.8	4.0
Tennessee Titans	12.1	8.6	3.4
Baltimore Ravens	11.9	8.9	3.1
Philadelphia Eagles	11.3	9.7	1.6
Washington Redskins	7.0	5.4	1.6
.
St. Louis Rams	2.6	4.3	-1.7
Kansas City Chiefs	4.4	6.2	-1.8
Arizona Cardinals	8.0	9.9	-1.9
Denver Broncos	6.2	8.5	-2.3
Detroit Lions	2.8	5.5	-2.7

Four wins.

Compare that to the 2.8 wins above average that the New Orleans Saints' offense had this year, the most in the league, and it's a no-brainer that the Steelers' defense is one of the all-time greats.

Really? Or is this just a case where the statistics lie?

I performed the same method using all teams since 1970. Whose defense reigns supreme? The '86 Bears or the Steel Curtain? Or someone else?

Here are the top-15 defenses of all-time.

All-time Defensive Wins Above Average
Year/Team	W	adj._W	diff
1971 Minnesota Vikings	10.8	6.2	5.2
2000 Baltimore Ravens	13.2	8.1	5.1
1975 Los Angeles Rams	12.1	7.7	5.1
1977 Atlanta Falcons	9.2	4.8	5.1
2002 Tampa Bay Buccaneers	12.5	8.0	4.5
1971 Baltimore Colts	12.0	8.2	4.4
2005 Chicago Bears	10.1	5.9	4.3
2000 Tennessee Titans	12.6	8.4	4.2
1986 Chicago Bears	12.9	8.7	4.2
2008 Pittsburgh Steelers	11.8	7.9	4.0
1970 Minnesota Vikings	12.2	8.8	3.9
1976 Pittsburgh Steelers	12.4	9.0	3.9
2006 Baltimore Ravens	12.5	8.6	3.9
1973 Miami Dolphins	12.1	8.9	3.7
2001 Chicago Bears	12.1	8.4	3.7

The 1971 Minnesota Vikings—also known as the Purple People Eaters—gave up under 10 points per game, which was almost half of the 1971 league average (19.4 points per game), and the 2000 Baltimore Ravens also gave up of the league average points per game (10.3 for Ravens' opponents, and 20.7 for the league).

And then—wait, the 7-7 1971 Atlanta Falcons had the fourth-best defense of all time?
Yep. They gave up a paltry 9.2 points per game, but only scored 12.8 per game; because their offense was more than four points per game under the league average, their defense had to carry their team to seven wins and an expected win total of more than nine.

Why are the 1986 Chicago Bears so low? They scored 22 points per game, more than the league average, so their offense accounted for some of their 14 wins.

The same can be said of the 1976 Pittsburgh Steelers, who scored 21.4 points per game in a 16.8-points-per-game league. Their defense was one of the best, but their offense was still almost five points above the league average.

The basic principle is simple: Your defense gets the most credit when your offense is terrible and you still perform like a playoff team. If you can reach the playoffs with a below-average offense like Pittsburgh, your defense must have carried you through the 14-10 games.

An all-time great defense?

Borderline top-10 is more like it.