Through the end of November, San Diego allowed opposing offenses an average of 7.2 yards per play on first down. That’s terrifying: The league average is just 5.4 yards per first-down play. They were more than a half-yard worse than the league’s second-worst defense over that time frame (Dallas). A league-high 29.7 percent of plays on first down against the Chargers gained 10 yards or more. But from Week 13 on, the Chargers basically retreated to league average, allowing 5.3 yards per play on first down. It was a December miracle.