It has been five years since the Steelers defense ranked No. 1 in the NFL — for the fourth time in six seasons — a reign not even the great Steel Curtain defenses of the 1970s could match.
Their dominance crumbled faster than the Berlin Wall. A steady decline began in 2013 when the Steelers defense collapsed from No. 1 the previous year to No. 13, then to 18 and then to No. 21 for the 2015 season.
The people who fueled those defenses got old and departed; some, like Troy Polamalu and their beloved coordinator Dick LeBeau, unwillingly.