PFF doesn't like the Seattle safeties
The Seahawks' defense overall seems much better than in several years past. Before the season, many talked about how deep Seattle's secondary would be with the addition of rookie cornerback Devon Witherspoon and Jamal Adams coming back. In the past three games, Seattle hasn't allowed more than 168 yards through the air in any single game. The argument could be made that Seattle has faced a few bad quarterbacks, but then that wouldn't be true because Seattle played Joe Burrow of the Bengals in Week 6.
In the first three games of the season, Seattle allowed at least 316 passing yards in each contest. It should be noted, however, that Jamal Adams did not return fully until Week 6. Plus, Witherspoon missed the first game of the year and Riq Woolen was still working his way back from a knee injury he suffered in minicamp. Also, Quandre Diggs and Julian Love didn't start the season playing very well.
This has factored into Pro Football Focus's (subscription required) grading of Seattle's safeties. Adams has a grade of 64.9 and that would rank 42nd in the NFL had he played enough snaps to qualify. The issue is that Adams' grade is almost 5 points higher than Seattle's second-highest-graded safety, Julian Love. Love is 60th overall in the league. Quandre Diggs is worse at 72.
The weird part is we can see with our own eyes and tell from the statistics that opposing offenses have put up for at least half the season so far that Seattle's safeties are not as bad as PFF's grades. Adams coming back has helped a bunch, but Diggs and Love are also playing better than they were in the first couple of games.