I recently looked at the history of teams to make a significant improvement from one year to the next and found that many of them win fewer games the year after their breakthrough season. This suggests that the Bears might be due for a bit of a letdown from their 12-4 record in 2018 (though they do match the profile of teams that generally stay good after making the jump.)
Today, I want to look more closely at Chicago’s underlying performance in 2018 to see if there’s anything there to suggest they are a team poised for a fall. This is closely modeled after work Bill Barnwell does every off-season, where he uses three factors to identify teams who are likely to improve and likely to regress.
Pythagorean Expectation
The first factor is called the Pythagorean expectation, and it is a measure of how many games a team is expected to win based on how many points they scored compared to how many points they allowed. The exact formula can be seen here, but the general idea is that truly good teams score a lot more points than they give up. Teams that win a lot of games without a large difference in points scored/allowed were considered more lucky than good and are likely due for a fall.
- 2018 Bears stats: 421 points scored, 283 points allowed, 12 wins
- 2018 Pythagorean expectation: 11.5 wins
The Bears didn’t significantly outperform their Pythagorean expectation, which means they won a lot of games because they were legitimately good, not lucky. So far, there is no reason to think that significant regression is coming.
Record in Close Games
The 2nd factor looks at how well teams performed in close games, which Barnwell defines as having a final scoring margin within 7 points. I think 8 points makes a lot more sense given that’s still a one possession game, but in this case it doesn’t change anything for the Bears, so we’ll stick with 7.
The idea here is that teams should finish around .500 in close games, and teams that finished significantly better than that are likely going to experience regression to the mean – and a corresponding decrease in wins – the following year.
In 2018, the Bears went 6-4 in games that finished within one score, which is not that far off from the expected 5-5 mark if it was truly random. Again, there’s nothing to suggest a huge drop-off is coming for the Bears here. And if you look more closely, you’ll see that Minnesota, Green Bay, and Seattle all scored meaningless points in the last 48 seconds of a two-score game to make the final score look closer. If you don’t consider those to truly be close games, the Bears finished 3-4 in one score games. Either way, they again match the profile of a team that was legitimately good, not one that got lucky.
Strength of Schedule
The final factor to look at is the strength of schedule. I should specify this is the schedule strength of teams faced the prior year, not the projected strength of schedule for the upcoming year, which has little relationship with how difficult a schedule will actually be. The idea here is that teams who played a schedule that ended up being easy the year before are likely going to face a more difficult schedule in the upcoming season, which will likely lead to more losses from playing better teams.
And here’s one area where the Bears do in fact show up like a lucky team that might be due for some regression. Their opponents in 2018 combined for a 0.430 win percentage, which was the lowest in the NFL over the last 5 years. So while their predicted 2019 opponent win % of 0.520 means absolutely nothing, it is all but guaranteed that the Bears will face a more difficult schedule in 2019 than they did in 2018.
But I’m not particularly worried about the strength of their schedule. In 2018, the Bears went 4-1 against teams who finished the season with winning records and 8-3 against teams who finished the season with losing records. They actually had a better track record of beating good teams than bad ones. Again, we see that the Bears were a legitimately good team in 2018, not a lucky one (even though their schedule was unusually easy).
Wrapping it Up
It’s possible, even likely, that the Bears will win fewer games in 2019 than the 12 they won last year, but there’s not really anything in their statistical profile to suggest that they are due to take a massive fall. They weren’t lucky, they were just really, really good, and they return almost everybody from that team, so there’s no reason to think they won’t be really good again.
