The Patriots and 49ers have lost a lot of defensive personnel over the last year or two. In San Francisco's case it's been a steady erosion of injuries, free agent losses, and retirements, while New England comes off a rough offseason. These defenses probably won't be as tough as they once were.
But I'm hesitant to say that suddenly either team will be a pushover. Both have been very good at stopping the run over the past decade. Only Pittsburgh and Baltimore have been consistently better. And that's with personnel changing plenty from season to season.
The table below shows how teams have ranked in run defense in each of the last 10 seasons, sorted by their total of top-10 finishes over that time frame. I think those teams will still be pretty good at the thing they've done best in recent years.
| DEFENSE VERSUS THE RUN, 2005-2014 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Team | '14 | '13 | '12 | '11 | '10 | '09 | '08 | '07 | '06 | '05 | Top 10s |
| Pittsburgh | 6 | 21 | 2 | 8 | 1 | 3 | 2 | 3 | 3 | 3 | 9 |
| Baltimore | 4 | 11 | 20 | 2 | 5 | 5 | 3 | 2 | 2 | 9 | 8 |
| San Francisco | 7 | 4 | 4 | 1 | 6 | 6 | 13 | 22 | 18 | 18 | 6 |
| New England | 9 | 30 | 9 | 17 | 11 | 14 | 15 | 9 | 5 | 8 | 5 |
| Chicago | 17 | 32 | 8 | 5 | 2 | 23 | 5 | 25 | 6 | 11 | 5 |
| Dallas | 8 | 27 | 22 | 7 | 12 | 4 | 12 | 6 | 9 | 15 | 5 |
| Minnesota | 25 | 16 | 11 | 11 | 9 | 2 | 1 | 1 | 1 | 19 | 5 |
| NY Jets | 5 | 3 | 26 | 13 | 3 | 8 | 7 | 29 | 24 | 29 | 5 |
| Denver | 2 | 8 | 3 | 22 | 31 | 26 | 27 | 30 | 11 | 2 | 4 |
| San Diego | 26 | 12 | 6 | 20 | 4 | 20 | 11 | 16 | 7 | 1 | 4 |
| Seattle | 3 | 7 | 10 | 15 | 21 | 15 | 18 | 12 | 22 | 5 | 4 |
| Arizona | 13 | 1 | 28 | 21 | 30 | 17 | 16 | 10 | 15 | 10 | 3 |
| Atlanta | 21 | 31 | 21 | 6 | 10 | 10 | 25 | 26 | 20 | 26 | 3 |
| Carolina | 16 | 2 | 14 | 25 | 23 | 22 | 20 | 18 | 10 | 4 | 3 |
| Cincinnati | 20 | 5 | 12 | 10 | 19 | 7 | 22 | 21 | 14 | 20 | 3 |
| Houston | 10 | 23 | 7 | 4 | 13 | 11 | 23 | 19 | 19 | 32 | 3 |
| Miami | 24 | 24 | 13 | 3 | 7 | 18 | 10 | 32 | 8 | 17 | 3 |
| NY Giants | 30 | 14 | 25 | 19 | 8 | 13 | 9 | 8 | 13 | 12 | 3 |
| Philadelphia | 15 | 10 | 23 | 16 | 16 | 9 | 4 | 7 | 26 | 21 | 3 |
| Washington | 12 | 17 | 5 | 18 | 26 | 16 | 8 | 4 | 27 | 13 | 3 |
| Detroit | 1 | 6 | 16 | 23 | 24 | 25 | 32 | 23 | 21 | 24 | 2 |
| Jacksonville | 27 | 29 | 30 | 9 | 22 | 19 | 13 | 11 | 4 | 14 | 2 |
| Tampa Bay | 19 | 15 | 1 | 32 | 28 | 32 | 19 | 17 | 16 | 6 | 2 |
| Tennessee | 31 | 20 | 24 | 24 | 20 | 12 | 6 | 5 | 30 | 22 | 2 |
| Green Bay | 23 | 25 | 17 | 14 | 18 | 1 | 26 | 14 | 12 | 23 | 1 |
| Kansas City | 28 | 22 | 27 | 26 | 14 | 30 | 30 | 28 | 17 | 7 | 1 |
| St. Louis | 14 | 9 | 15 | 31 | 17 | 27 | 29 | 20 | 31 | 28 | 1 |
| Buffalo | 11 | 28 | 31 | 28 | 32 | 31 | 21 | 24 | 28 | 31 | 0 |
| Cleveland | 32 | 18 | 19 | 30 | 27 | 28 | 28 | 27 | 29 | 30 | 0 |
| Indianapolis | 18 | 26 | 29 | 29 | 25 | 24 | 23 | 15 | 32 | 16 | 0 |
| New Orleans | 29 | 19 | 32 | 12 | 15 | 21 | 17 | 13 | 23 | 27 | 0 |
| Oakland | 22 | 13 | 18 | 27 | 29 | 29 | 31 | 31 | 25 | 25 | 0 |
--Andy Richardson