If there is a historical pattern for the Pittsburgh Steelers defense in most of their previous Super Bowl wins, it is one of not performing as well during the title tilt as they did during the rest of the season.
Four examples of this include:
Super Bowl X: Pittsburgh had allowed only 10 touchdown passes in the 16 regular-season and postseason games preceding the Super Bowl, and only four of those were of a length greater than 20 yards. Roger Staubach and the Dallas Cowboys' pass catchers connected on touchdown throws of 29 and 34 yards.
Super Bowl XIII: The Steelers had not allowed a first-quarter touchdown all season long and gave up one to Dallas. They also had not given up more than 24 points in a single contest that year and allowed 31 to the Cowboys.
Super Bowl XIV: Vince Ferragamo, a quarterback with only seven career starts and 205 career passes to his credit at that point, led the Rams to a 19-17 lead after three quarters.
Super Bowl XLIII: The Black and Gold allowed only nine touchdown passes in the 11 games prior to the Super Bowl and gave up only 16 for the entire season and playoffs, but let Kurt Warner throw three scoring aerials in this contest.
This type of thing would normally be seen as historical happenstance -- except, there are multiple reasons to believe the current Steelers' pass defense is not anywhere near as good as its second-ranked 73.1 passer rating allowed would indicate.