Nickel defense is the new base, and it has been for a while. With the league trending ever more pass-happy, most NFL defenses have been using five or more defensive backs at an ever-increasing rate. The Seattle Seahawks, on the other hand, decided to stand pat in base defense last season.
While the league average saw an extra defensive back on the field on 72.8% of snaps, Seattle left base defense just 31.2% of the time, a rate more than 30 percentage points lower than any other team in the league. So why did they do that, and why didn’t it cost them as badly as we would assume being perpetually hampered with an extra linebacker in coverage would?