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Navigating Bear Markets: Breaking the QB Record Books

What will it take for Justin Fields to re-write the Bears record books for rookie QB’s?

Chicago Bears

49. 

The Chicago Bears have started 49 different quarterbacks since the NFL-AFL Merger (1970). That is 49 quarterbacks across 51 seasons. Shockingly, the Bears drafted just 14 of those 49 players, and only six of them went on to play any significant snaps in their rookie years.

  • Bob Avellini (1975)
  • Jim McMahon (1982)
  • Cade McNown (1999)
  • Craig Krenzel (2004)
  • Kyle Orton (2005)
  • Mitchell Trubisky (2017)

So what is the point here? The point is that the Bears’ rookie QB records are weak for such a historically significant franchise. Further, the point is that Justin Fields has a real chance to break the Bears record book when he (eventually) gets onto the grass.

In this installment of Navigating Bear Markets, I will outline where Bears rookie QB records currently stand and identify the areas in which Justin Fields has a chance to etch his name. As always, you can follow on Twitter @ButkusStats. Additionally, previous installments of Navigating Bear Markets can be found HERE.

Bears Rookie QB Records – Per Game

Initially, I was looking at the typical volume stats such as total yards, total TDs, etc. As I was compiling data, I came to realize that rookie stats are rarely one-size-fits-all, and typical volume stats do not tell a very clean story. For that reason, I decided to look at per-game stats instead of season stats.

In the below table, I have listed all QB’s that have started five-plus games for the Bears in their rookie year. The green highlights represent the current Bears record-holder for each stat.

Then, there is a row titled “CHI Threshold”. “CHI Threshold” represents the Bears current rookie record threshold for each stat.

Below the threshold row, I have listed every QB drafted in the first round from 2015-2020 that surpassed the Bears’ current record. The green highlights in these rows mean that the QB surpassed the Bears record for that stat. The red highlights mean that the QB failed to surpass the Bears record for that stat.

  • There were 20 QB’s drafted by any team in the first round from 2015-2020. However, the Bears drafted one of those QB’s (Michell Trubisky), and two QB’s did not play as rookies (Patrick Mahomes, Jordan Love). Because of those circumstances, we will push the population down to 17 QB’s.
  • Four QB’s (24%) since 2015 would have broken the Bears’ rookie record for passing yards per game (Justin Herbert, Joe Burrow, Baker Mayfield, and Jameis Winston). If we expand this to include rushing yards, then Deshaun Watson would also break the record. In doing that though, Winston would fall short of the current Bears record.
  • Six QB’s (35%) would have broken the Bears’ rookie record for pass TD’s per game (Herbert, Mayfield, Watson, Winston, Daniel Jones, Marcus Mariota). If we expand this to include rushing TD’s, then nine different QB’s (53%) would have broken the Bears record.
  • Only three QB’s (18%) broke the Bears’ rookie record for interceptions per game (Burrow, Lama Jackson, Tua Tagovailoa). I also added in fumbles at an assumed fumble lost rate of 45% (NFL average for past ten years) to generate turnovers per game. Only Herbert and Burrow (12%) would have broken the Bears record in the turnover category.
  • Therefore, it appears that breaking the yardage records on a per-game basis could be a tall order for Justin Fields. While it has happened in recent history, I think expectations for him should be set below the likes of Herbert, Mayfield, Burrow, and especially Watson due to his ridiculous and short-lived rookie season. That being said, Fields could certainly break the total yardage record for the Bears (2,193 passing yards, 2,245 total yards) if he starts early in the season.
  • The touchdown per game records are more within reach for Fields, with 35% of the rookie QB’s drafted since 2015 having theoretically broken through the Bears record book. The Bears’ records for rookie QB TD’s over the course of a full season is also well within reach (nine passing TD’s, ten total TD’s).

Bears Rookie QB Records – Rate Stats

This chart follows a similar concept, but instead of looking at per-game stats, we are looking at rate stats. The stat titled “+20% EPA” represents EPA/Play when filtering out plays when win probability was below 20% or above 80%. This method toward displaying EPA per play aims to give context to garbage time stats. A QB who has strong EPA per play but declines significantly when applying the 20% win probability filter likely pads stats late in games.

Additionally, I am utilizing a stat that I have used for the past few years here that I call “Total Adjusted Net Yards per Play“ (TANY/P). This stat roots from the passing stat “Adjusted Net Yards per Attempt” (ANY/A) and aims to incorporate rushing numbers into the equation. 

ANY/A = (Pass Yds + Pass TD’s * 20 – INT’s * 45 – Sack Yds) / (Pass Att’s + Sacks)

The concept with ANY/A ultimately comes down to the value of a touchdown and the value of a turnover. Introduced and explained in a book called “The Hidden Game of Football”, ANY/A is currently calculated by deeming a touchdown to be worth a 20-yard gain and a turnover to be worth a 45-yard loss. You can find further discussion around the reasoning here.

So in order to add in rushing production, I simply add in rush yards, rush TD’s, rush attempts, and fumbles with an assumed fumble lost rate of 45% based on historical figures. 

TANY/P = (Pass Yds + Rush Yds + Total TDs * 20 – Total Turnovers * 45 – Sack Yds) / (Pass Att’s + Rush Att’s + Sacks)

  • Nine QB’s (53%) since 2015 would have broken the Bears rookie record for completion percentage.
  • Only four QB’s (24%) would have broken the Bears rookie record for yards per attempt (Y/A). Expanding on yards per attempt to include rushing stats (yards per play) creates a very different result. Eight QB’s (47%) surpassed the current Bears record in their rookie seasons.
  • Adding in other factors by using ANY/A garners very different results, as twelve QB’s (71%) would have broken the Bears rookie record for ANY/A. When taking rushing production into account by using TANY/P, that pool shrinks to eight QB’s (47%).
  • The Bears QB Rating record for rookies is similar to ANY/A, as ten QB’s (59%) would have set a new record in their rookie seasons.
  • Looking at the TD:TO ratio, only four QB’s (24%) have surpassed the current Bears rookie record of 1.34.
  • A whopping 14 QB’s (82%) have exceeded the Bears’ current rookie record for EPA per play. This stat only goes back to 1999, so the record does not include rookie seasons for McMahon or Avellini.
  • Similarly, 13 QB’s (76%) have exceeded the Bears rookie record for EPA per play when applying the 20% win probability filter.
  • Justin Fields has a strong chance to break a lot of the Bears’ existing rookie records for rate stats.

Bears Rookie QB Records Adjusted for Era

This chart attempts to project how each of the Bears’ rookie seasons noted above would project to the 2020 season based on league averages. In order to do this, we start by looking at Pro Football Reference’s advanced passing stats. For these stats, league average is valued at 100. For example, Jim McMahon had ANY/A+ of 100 his rookie year, which means that he was equivalent to league average in ANY/A. In order to get the era-adjusted ANY/A figure, I simply matched his ANY/A+ to a 2020 QB with the same ANY/A+. Long story short:

ANY/A+ of 100 in 1982 =  ANY/A of 4.9

ANY/A+ of 100 in 2020 = ANY/A+ of 6.8

Jim McMahon’s rookie ANY/A projected to 2020 = 6.8

  • Two QB’s (12%) since 2015 would have broken the Bears existing era-adjusted completion percentage record. The same rate is applicable to era-adjusted QB Rating and ANY/A. These three categories are unlikely for Fields to break, but not impossible.
  • Only one QB (6%) has broken the existing era-adjusted yards per attempt and INT %. These stats appear to be a long shot for Fields to reach.
  • Not a single rookie QB drafted since 2015 has met the Bears era-adjusted rookie record for TDs:INTs (currently held by McMahon).
  • Four QB’s (24%) have broken the Bears era-adjusted record for TD % and sack %.
  • The majority of the era-adjusted metrics are generally out of reach unless Fields blows us all away his rookie year. Jim McMahon and Bob Avellini play spoiler here for most of these stats.

Summary

Rookie records likely to be broken (50%+ of rookie QBs since 2015 have broken):

  • Completion % (Bears rookie record = 59.4%)
  • ANY/A (Bears rookie record = 5.05)
  • QB Rating (Bears rookie record = 79.9)
  • EPA per Play (Bears rookie record = -0.077)
  • 20% WP EPA per Play (Bears rookie record = -0.054)

Rookie records within reach (30%+ of rookie QBs since 2015 have broken):

  • TD’s per game (Bears rookie record = 1.3)
  • Yards per Play (Bears rookie record = 5.58)
  • TANY/P (Bears rookie record = 4.88)

Rookie records that may be out of reach (< 30% of rookie QBs since 2015 have broken):

  • Passing yards per game (Bears rookie record = 244 yards)
  • INT’s per game (Bears rookie record = 0.6)
  • Total yards per game (Bears rookie record = 255 yards)
  • Yards per attempt (Bears rookie record = 7.48)
  • TD’s : TO’s (Bears rookie record = 1.34)
  • Era-adjusted TD % (Bears rookie record = 5.2%)
  • Era-adjusted sack % (Bears rookie record = 6.1%)

Not going to happen (<15% of rookie QB’s since 2015 have broken):

  • Turnovers per game (Bears rookie record = 0.9)
  • Era-adjusted completion % (Bears rookie record = 65%)
  • Era-adjusted yards per attempt (Bears rookie record = 7.9)
  • Era-adjusted INT % (Bears rookie record = 1.5%)
  • Era-adjusted QB Rating (Bears rookie record = 97)
  • Era-adjusted ANY/A (Bears rookie record = 6.8)

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