Author: Connor Loughlin (Medill ’20)

Stats Valid As of October 5, 2018

Heading into their bye week at 3-1 and riding a convincing three-game win streak, the Chicago Bears have opened eyes around the league and are surprisingly sitting atop the NFC North at the season’s quarter mark.

 

That 3-1 record could realistically be 4-0 if not for a bit of Aaron Rodgers late game heroism, but might arguably be 1-3 had Ryan Pace not made the aggressive move to trade for Khalil Mack a week before the start of the regular season.

 

Despite the dazzling start, many questions remain about these young Chicago Bears who are currently second in point differential behind the dominant Los Angeles Rams.  Most of these questions center around inexperienced second-year quarterback Mitchell Trubisky, who finally had his breakout game with 6 TD’s and a raw QBR score of 98.9 against a weak Tampa Bay secondary.

 

Needless to say, nobody expects Trubisky to be as dominant over the last 12 games as he was in Week 4.  The appropriate question is whether Trubisky can be better than his subpar play during the first three weeks of the season.

 

The Bears defense currently ranks first in the league in Football Outsider’s DVOA rankings by a pretty considerable margin.  With supreme talent littered at every level of the defense, it is pretty safe to assume that this group will finish in the top five come season’s end barring significant injuries to players such as Khalil Mack, Akiem Hicks and Eddie Jackson.

 

Should the Bears defense remain as dominant as they project, it begs the question: how good must Trubisky be for this team to truly contend?  A basic presumption would suggest that his play should fall somewhere between his performances in the first three weeks and his performance in Week 4 against Tampa Bay, but this is a very wide range.

 

To answer this question, I gathered some data from the past five NFL seasons and charted the performances of quarterbacks on every single team who finished in Football Outsider’s top 5 defenses based on DVOA rating.  I then created a scatterplot of each starting quarterback’s total QBR for the season versus the amount of games the team won that season.

 

There were a couple teams who used multiple quarterbacks for a similar amount of passing attempts during the regular season: the 2015 Denver Broncos (Manning and Osweiler) and the 2017 Arizona Cardinals (Palmer, Stanton and Gabbert).  For these teams I created a weighted average of each quarterback’s total QBR.

 

I ran a linear regression for the scatterplot and the results are below.

Year	Team	DVOA Defensive Rank	Starting QB’s	Total QBR (x)	Team Wins (y)	Playoffs
2013	Seattle	1	Russell Wilson	67.2	13	Y
2013	Arizona	2	Carson Palmer	54	10	N
2013	Carolina	3	Cam Newton	64.3	12	Y
2013	Buffalo	4	EJ Manuel	38.2	6	N
2013	Cincinnati	5	Andy Dalton	54.8	11	Y
2014	Seattle	1	Russell Wilson	69.7	12	Y
2014	Buffalo	2	Kyle Orton	44.5	9	N
2014	Detroit	3	Matt Stafford	44.7	11	Y
2014	Denver	4	Peyton Manning	72.6	12	Y
2014	San Francisco	5	Colin Kaepernick	58.1	8	N
2015	Denver	1	Manning/Osweiler*	49.2	12	Y
2015	Carolina	2	Cam Newton	61.4	15	Y
2015	Arizona	3	Carson Palmer	76.4	13	Y
2015	Seattle	4	Russell Wilson	68.6	10	Y
2015	New York (A)	5	Ryan Fitzpatrick	62	10	N
2016	Denver	1	Trevor Siemian	49.7	9	N
2016	New York (N)	2	Eli Manning	45.7	11	Y
2016	Arizona	3	Carson Palmer	52.9	7	N
2016	Philadelphia	4	Carson Wentz	46.7	7	N
2016	Seattle	5	Russell Wilson	57.1	10	Y
2017	Jacksonville	1	Blake Bortles	59.2	10	Y
2017	Minnesota	2	Case Keenum	72.8	13	Y
2017	Baltimore	3	Joe Flacco	46.7	9	N
2017	Arizona	4	Palmer/Gabbert/Stanton*	41	8	N
2017	Philadelphia	5	Carson Wentz	78.5	13	Y

 

There is an evidently positive correlation between the level of quarterback play and team wins for teams with elite defenses, which was to be expected.  The R² value of 0.4672 suggests that there are several extraneous variables that impact a team’s wins outside of quarterback play, yet the level of quarterback play does account for a significant amount of variance in games won.

 

Teams with a top five DVOA defense during the last five years have won an average of 10.44 games, which would typically be sufficient enough to garner a playoff spot.  15 of these 25 teams ended up making the playoffs, and three of the last five Super Bowl champions have had a top five defense based upon DVOA.

 

The numbers are on Chicago’s side to make a playoff run.  That being said there are still 12 games left to be played and a lot can change.  Should the Bears defense remain elite over the course of the season, how well must Trubisky play in order for the Bears to make the playoffs?

 

Through four games Trubisky has posted a QBR of 54.8 (50 is considered to be relatively league average), but this number is heavily skewed by his performance against Tampa Bay.  Here are some Total QBR scores and their corresponding expected win totals garnered from the regression line above.

 

 

Season Total QBR Score	Expected Wins
40	8.1417
45	8.8007
50	9.4597
55	10.1187
60	10.7777
65	11.4367
70	12.0957
75	12.7547
80	13.4137

 

Trubisky certainly does not have to be great in order for the Bears to make the playoffs and potentially win the NFC North, but he must be much better than his mediocre first three weeks.  If extrapolated to a full season, his current total QBR of 54.8 would result in an expected win total of roughly 10.09.

 

While 10 wins usually puts you in contention for a playoff spot, it certainly does not guarantee you the opportunity to play January football, especially with the guy playing quarterback about 200 miles north within your division.  Trubisky will have to raise his game as the season progresses in order for the Bears to win important divisional and conference games and fight off both Minnesota and Green Bay for the division title.

 

Realistically, Trubisky has to be at least as good as Blake Bortles was for the Jacksonville Jaguars last year in order for the Bears to feel confident about a playoff berth.  In 2017, Bortles posted a respectable but modest 59.2 total QBR which resulted in 10 wins for a Jaguars team that almost made a Super Bowl behind the league’s best defense.  According to the model a 59.2 total QBR results in roughly 10.67 expected wins.

 

Even if Mitchell fails to live up to the hype for the rest of 2018 resulting from the electrifying play of Patrick Mahomes and Deshaun Watson, it should not be a problem for the Bears.  Their defense is good enough to keep them squarely in the playoff picture for the remainder of the year.

 

However, should Trubisky continue to show steady improvement in Matt Nagy’s offense this year and beyond to compliment a young and ultra-talented defensive core that is more or less locked up for the next few years, the Bears could find themselves as a perennial playoff contender.