The ascension of the San Francisco 49ers’ defense from the NFL's worst unit by PFF grade in 2018 to one of the best defenses in the league this season — regardless of the metric that you look at — is arguably the biggest turnaround by any group in the NFL this year. The massive improvements to their pass defense were the driver of that rise, and they can be attributed to two areas: coverage and pass rush.
It’s hard to overstate how important their back-end improvements have been. Richard Sherman has come back from an Achilles injury that ended his 2017 season to be named PFF’s top coverage defender in the NFL in 2019. From the free safety position, Jimmie Ward has helped spearhead a defense that has effectively eliminated the downfield passing game for opposing offenses. K’Waun Williams has played like one of the top slot cornerbacks in the NFL. Their coverage has been outstanding, and on a macro level, coverage is more important than pass rush.
The pass rush deserves its fair share of love, as well, though. In the case of the 49ers’ 2019 season, the steps taken by both groups have benefited each other. The 49ers have the third-highest team pass-rushing grade in the NFL this season, leaps and bounds above their 27th-ranked group a season ago. The scary part for the Kansas City Chiefs in Super Bowl LIV is that the 49ers’ best four-man rush is healthy now after not being together for much of the year. And folks, I’m here to tell you that group can cause some damage.