The 49ers have the best defense in football and the numbers back it up
I wanted to start by comparing the drives that went the worst for the defense. So I compared all drives that ended on the defense’s side of the field inside the 40-Yard line.
All Defensive Drives That Ended Inside Defense’s 40-Yard Line
| Team | Drives | YDS Per Drive | Punt % | Score % | TO % | Downs % | Missed FG% | AVG Start |
| 49ers | 40 | 47.7 | 0.0% | 60.0% | 15.0% | 20.0% | 5.0% | 38.0 |
| Patriots |
27 | 52.0 | 0.0% | 59.3% | 22.2% | 11.1% | 7.4% | 26.6 |
| League | 1710 | 52.8 | 2.6% | 74.9% | 8.9% | 5.9% | 7.5% | 33.6 |
Looking at the rate stats, the 49ers are preventing scores on nearly as many drives, but are failing to generate turnovers at New England’s rate. But, before I went any further in my analysis I wanted to make sure I was looking at drives when the game was relatively close.
Both teams have dominated opponents so much, I wanted to limit the number of garbage time drives in the sample. So I added a filter to only include drives when the margin was less than 15 points at the start of the drive.
All Defensive Drives That Ended Inside Defense’s 40-Yard Line With Margin <15
| Team | Drives | YDS Per Drive | Punt % | Score % | TO % | Downs % | Missed FG% | AVG Start |
| 49ers | 35 | 47.9 | 0.0% | 62.9% | 14.3% | 17.1% | 5.7% | 38.8 |
| Patriots |
19 | 56.6 | 0.0% | 68.4% | 10.5% | 10.5% | 10.5% | 22.6 |
| League | 1484 | 53.3 | 2.6% | 75.9% | 8.3% | 5.5% | 7.6% | 33.0 |
All of a sudden, the 49ers are preventing scores and generating turnovers at better rates than New England. It’s not clear why the Pats opponents have missed field goals at nearly twice the rate of the 49ers opponents.
Assuming those discrepancies are random and not a side-effect of the defense’s play, those missed field goals are making the differences look even smaller than they should be.
The easy retort is that the 49ers have allowed 16 more drives inside their own 40. Who cares what happens on the drives that get there? If the opponent’s offense consistently gets deeper in your territory it’s going to cause problems.
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Furthermore, while the 49ers are allowing fewer yards per drive, when you take into account the average starting field position, it becomes clear that the fewer yards could just be a symptom of their opponents starting with less yards to go for the endzone.
That discrepancy caught my attention though. The defense doesn’t control where their opponents get started and on these drives 49ers opponents are starting just inside their own 40, while New England’s opponents are inside their own 23.
I suspected the disparity might have had something to do with this:
| Team | Offensive Turnover % |
| 49ers | 13.0% |
| Patriots | 6.6% |
49ers fans can (and will) defend Garoppolo all they want, but he has thrown many more interceptions than Tom Brady (10 to 5) and many of Garoppolo’s picks have come in 49ers territory.
How do these defenses compare when their offenses don’t put them in poor field position?