Let’s review the season of a mystery team from last year. This team had a pretty difficult schedule, but wound up with an average record. Here is how things broke down, starting with the good.

Mystery team played two home games against teams in the bottom quarter of the league (all team ratings in this post are using SRS). Those are the games where an average team should do well, and in fact, those were the only two games all year that the team won by double digits.

Mystery team had three other games where an average team would be “expected” to win based on strength of opponent and game location: Mystery team went 3-0 in those games, with an average margin of victory of 5.3 points.

But things were not so simple for our mystery team all year.

Mystery team played five games against teams in the top quarter of the NFL. The result? An 0-5 record, with an average margin of defeat of 16.4 points.

The remaining six games were ones where an average team would be “expected” to lose based on strength of opponent and game location, but were not against top-8 teams. Mystery team had an average points differential of -3.7 in those games, and a 2-4 record.

To recap, Mystery team blew out the bad teams, beat the below-average teams, lost to the above-average teams, and was blown out by the great teams. That, I think, is as unexciting as a season narrative can get. But if a team goes 1-7 to start the season, and then 6-2 to finish, it’s easy to spin the “tale of two halves” narrative.

Yes, our Mystery team was the Detroit Lions. Those three games against top-5 teams came against Seattle, Arizona, and Kansas City: those games were all in the first half of the schedule, and the Lions lost 13-10, 42-17, and 45-10. It was in the second half when Detroit got to host Philadelphia and San Francisco, with the Lions winning 45-14 and 32-17. In the first half, Detroit played Minnesota twice and Denver; in the second half, the Lions faced Oakland, New Orleans, and the Rams.

Did the Lions improve from the first half to the second half of the season? Sure. The graph below shows how the Lions did relative to expectation, based on home field and the strength of the opponent. In general, the trend was positive — i.e., Detroit got better as the season progressed:

In the first half of the year, the only really good game the Lions played was in Seattle, and that one is arguably misleading because Seattle wasn’t playing very well that time of year, either. But in general, strength of schedule played a big role in Detroit’s resurgence: the three wins in December came against the Saints, 49ers, and Bears: New Orleans finished last in points allowed, San Francisco finished 32nd in points scored, and the Bears game was a week 17 contest that featured Marc Mariani and Josh Bellamy as Chicago’s starting wide receivers.

To be fair, Detroit nearly went 7-1 down the stretch, with one loss coming on a Hail Mary. The Lions were a competent — and borderling good — team for the last eight games of the season. But I can’t help but think a lot of the team’s Jeckyl and Hyde act was the result of Splits Happen and strength of schedule.