Never.
That's how many times in 24 years a Wade Phillips- coordinated defense has allowed the NFL's fewest yards for an entire season. His units boast six top-five finishes, among them No. 2 rankings by New Orleans in 1983 and by Houston in 2011. A Denver defense has never accomplished the feat.
The Broncos will enter Sunday on the league's top perch. It would take a catastrophic performance to prevent them from finishing first. Denver is allowing 280.9 yards per game (4,213 overall). Seattle ranks second at 295.7 per game (4,436 overall). Denver also has a chance to become the first team since the 1991 Philadelphia Eagles to lead the NFL in pass, run and total defense.