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Bears at the Bye: The Best Defense in Football? Sure Seems That Way…

| October 10th, 2018

Chicago’s defense has been awesome in the first month of the season. They’re among the best in the league in nearly every category that matters, and are ranked first overall in DVOA. Now I want to look a little more closely at how well they’re performing against both the run and pass in different areas of the field.


Defending The Run

Chicago’s run defense was solid in 2017, but it has been fantastic so far in 2018. They have shut opposing run games down, and they’ve done it pretty much across the board, as we can see below.

Here’s the data for Chicago’s rushing defense by zone, courtesy of the NFL Game Statistics and Information System. The line at the bottom is the line of scrimmage, runs are split into 7 zones, and attempts and yards per carry are listed for each zone, with ranks relative to the rest of the NFL in parentheses. The height of the bar is proportional to yards per carry, and bars are colored green for top 10, red for bottom 10, and yellow for middle 12. Note expected yards per carry varies by region, so the colors are relative to their peers in that region.

A few thoughts:

  • That’s a whole lot of green. Awesome. Last year’s version featured a lot more yellow and red. This is a good time to remind you that Khalil Mack is an elite run defender in addition to being one of the best pass rushers in the league.
  • Speaking of Khalil Mack, he and Akiem Hicks usually line up opposite the RG and RT. Notice where defenses are running towards? There are 38 runs to the left side – away from Mack and Hicks -compared to 21 towards them on the right.

  • About that one red spot on the right end: that’s basically due to QB scrambles. According to the Pro Football Reference Game Play Finder, 3 of those 8 runs are QBs scrambling, and they account for the 2 longest runs. Remove those 3 scrambles and the average for the other 5 runs off right end is 4.4 yards per attempt, which is solid for outside runs.
    • This shows the limitations of small sample sizes when we split up only four games’ worth of data into so many different subsets.
    • It also illustrates the perils of having two pass rushers selling out to get the QB on the right side, but I don’t want to see Mack or Hicks hold back and focus more on contain. Keep hunting quarterbacks, it’s working.

Defending The Pass

Now let’s look at how Chicago’s pass defense has fared in various zones of the field. The figure below shows the number of plays, completion percentage, and yards per attempt for 6 zones. Each zone is colored according to the average of the yards per attempt and completion percentage (green = top 10, red = bottom 10, yellow = middle 12).

A few thoughts:

  • Again we see a lot less red than last years’ version. And that’s before you account for interceptions. The Bears already have 8 this year, matching their total from each of the past three seasons. That’s something I said before the season they needed to do, and it’s a big reason they’re winning games. Thanks Khalil Mack!
  • Kyle Fuller took a lot of flack early on this year for giving up a deep TD in each of the first two games, but he plays almost exclusively on the right side (more on that in the next article), and you can see that Chicago’s pass defense is at its best on his side for the 2nd year in a row.
  • Looking at passes over the middle, the overall numbers look bad, but I think that’s a bit deceiving. For starters, much of that came in week 1, when Roquan Smith wasn’t playing and Nick Kwiatkoski was terrible. Green Bay’s QBs combined to go 10/11 for 163 yards, with 1 TD and 1 INT, on passes to the short middle (all stats in these last 2 bullet points from the Pro Football Reference Game Play Finder). In the 3 weeks since, QBs have gone 14 for 17 for 115 yards to that zone. That’s still completing a lot of passes, but they’re not going anywhere (less than 7 yards per completion), and they’re not doing any damage (0 touchdowns, 6 1st downs, 4 of which were by Jameis Winston in garbage time in week 4. In short, I think this is more a function of one bad game with a backup getting picked on and not something to be particularly concerned about going forward.
  • Some of that comes from the Bears sitting in soft coverages that leave that zone as the most exposed late in games since they have the lead. That happened a good bit with Jameis Winston (5/5, 43 yards, all in garbage time) and Russell Wilson (5/5, 41 yards in garbage time). If we avoid garbage time by looking only at plays from the first 3 quarters since Roquan Smith started playing in week 2, teams are 6 for 9 for 44 yards throwing short middle. I think that’s a pretty solid argument that this is largely a function of the Bears funneling passes to this zone in prevent defense, which they’ve played a lot of since they’ve been winning (often by 2+ scores) late in games.

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