LAKE FOREST, Ill. -- The Chicago Bears' unexpected decline in 2019 is not strictly limited to offense.
Sure, Chicago's offensive ineptitude dominates the headlines, but its still formidable defense has gradually fallen off since traveling to London in Week 5.
Before that game against the Oakland Raiders, the Bears' defense looked nearly identical to last year's unit that led the league in total takeaways (36), interceptions (27), lowest passer rating (72.9), fewest first downs allowed (278), fewest rushing touchdowns (5), fewest rushing yards per game (80) and fewest total plays allowed of 20-plus yards (46).
Even after decorated defensive mastermind Vic Fangio left in the offseason to become the Denver Broncos coach, there was little reason to believe the Bears would experience much decline.
And the first month of the 2019 season felt like business as usual.
As Matt Nagy’s team opened the year 3-1, Chicago’s defense -- coordinated by former Indianapolis Colts coach Chuck Pagano -- ranked second in scoring defense, second in fewest yards per rush and fourth in fewest yards per play, and its 17 sacks trailed only the New England Patriots and Carolina Panthers (18), according to ESPN Stats and Information research.
The Bears gave up 11.3 points per game, 4.5 yards per play, 3.0 yards per rush and allowed opponents to convert on third down 27% of the time.
But during the team's current four-game losing streak, the Bears are surrendering 24.8 points per game, 5.4 yards per play and 4.2 yards per rush, per ESPN Stats and Information research. Over that four-game span, the defense has sacked the quarterback only six times while opponents have successfully converted 42% of third downs.
The Eagles converted four critical third downs on the final possession for their 22-14 win over the Bears last Sunday.
"It was very uncharacteristic of us," Bears cornerback Prince Amukamara said. "I feel like that is how it has been the entire year, with us not getting off the field. We have to correct that."
One explanation is simple wear and tear. The defense often stays on the field far too long because the offense can't sustain drives. In the Philadelphia game alone, the defense played 84 total snaps. The offense, by comparison, ran just 44 plays.
However, there's no denying the Bears miss Pro Bowl defensive tackle Akiem Hicks, who went on injured reserve with an elbow injury he suffered early in the Oakland game.
Using ESPN’s Pass Rush Win Rate powered by NFL Next Gen Stats, the Bears defeated their blocks within 2.5 seconds 57.4% of the time when Hicks was on the field this season, compared to 43.8% when Hicks was off the field.
For context, going from 57.4% to 43.8% is the difference between leading the NFL in that metric and being 18th-best in 2019. Furthermore, all eight of the rushing touchdowns allowed by the Bears this year have come when Hicks was off the field.
"When you lose somebody that has the size that he has, the personality that he has, that is a big loss," Nagy said. "... I mean, I think our defense is playing really well right now. There's times they can be better, but all that said, losing a Pro Bowl-caliber player like him, you're definitely going to lose a little bit."
That being said, the Bears' defense still ranks favorably through Week 9 when compared to last year’s juggernaut. In 2018, the Bears' defense was fourth in yards per play, third in total opponent QBR, fourth in points per game and fifth in yards per rush. This season, Chicago is once again fourth in yards per play, ninth in total opponent QBR, sixth in points per game and fourth in yards per rush. The big difference is in the takeaway department. The Bears have forced 11 turnovers compared to 21 at this time last year.
"... Red area, you know, our percentage is not bad, but this time last year I think they only had 15 or 16 possessions that they had to defend in the red area," Pagano said. "We are at 30. So that comes back to situational football, that comes back to third down. We aren't giving up [explosive plays], we are pretty good against the big play."
But Pagano knows the defense is capable of more.
"I think it's just a matter of cleaning up, cleaning up some things like penalties," Pagano said. "We had one defensive offside through eight games last year -- we got 10 [this season]. ... So if you eliminate that stuff and you make people [take] the long, hard way, then we will be better."