CHICAGO – Since Mike Zimmer and Kirk Cousins joined forces, the Vikings have become November's team.

Can they turn the corner this December?

Two mediocre performances in consecutive victories raise these questions:

Can Zimmer keep it up?

Will Cousins let him?

Zimmer has coached the Vikings long enough — nearly eight seasons now — for a few trends to emerge. His best month is November, in which he has built a 20-11 record. In the past few years, his teams have regressed in December.

In 2017, the Vikings went 4-1 in December during Zimmer's one superlative regular season.

After signing Cousins in 2018, Zimmer's teams went a combined 5-9 in the Decembers of 2018, 2019 and 2020.

Zimmer entered this December likely needing a strong month to have even an outside chance to make the playoffs and, theoretically, keep his job.

The month began with the Detroit Lions earning their first victory of the season against the Vikings.

In Game 2, the Vikings led 29-0 before needing a last-second defensive play to beat the Steelers 36-28.

Were the Vikings collapsing again?

It might be hard to tell. Their 17-9 victory over Chicago on Monday night was ugly, meaning the Vikings' two-game December winning streak feels as much like a warning as an accomplishment.

The 2021 Vikings are 7-7 with one more December game this season: Sunday at U.S. Bank Stadium against the Los Angeles Rams.

It's hard to tell how important this game is. Theoretically, the Vikings could lose Sunday, win the last two games of the season and sneak into the playoffs. It will provide a good test of this Vikings team, and Zimmer's ability to manage them in an important game late in the season.

As Vikings coach, Zimmer is 16-18 in December. That's his worst record in any month.

Why would his teams underperform in December?

Here are two unproven and unprovable theories.

Theory No. 1: Zimmer is naturally grumpy and his mood usually worsens late in the season. He hasn't achieved his goal of winning a Super Bowl in Minnesota, his team has gotten blown out in playoff games and he has faced questions about his job security since 2019. Grumpiness is an understandable if less-than-helpful reaction.

Theory No. 2: Quarterback Kirk Cousins' splits reveal that he is at his worst in December. His career passer ratings by month: September 94.7, October 98.3, November 109.8, December 91.4. It's easily his worst month for completion percentage (63.4%), despite it also being the month in which his passes travel the shortest distance (7.0 average yards per attempt).

He's won seven of his 16 December starts for the Vikings.

This season reflects these trends, and their personalities. If Zimmer is grumpy, Cousins is robotic. Both seem capable of tightening up in a tough situation.

Neither seems like the kind of guy you'd like to spend months of meetings with — and that could have been said before Cousins made it clear he won't get vaccinated to make life easier on the franchise that is paying him many tens of millions.

The Vikings' two most impressive performances this season were consecutive November victories against the Chargers and Packers.

Their two December victories were near-embarrassments against Pittsburgh and Chicago.

What might be most concerning about this trend is the play of Cousins.

He was excellent against the Chargers and Packers, completing a combined 49 of 72 passes for 635 yards, five touchdowns and zero interceptions.

Against the Steelers and Bears, he completed a combined 26 of 55 passes for 303 yards, four touchdowns and three interceptions.

Three games ago, he put up impressive numbers in a loss to the Lions, but the yards and touchdown passes came too late.

This has been a horrific three-game stretch for a highly paid and previously efficient quarterback. Cousins has thrown six interceptions this year, half of those in the past two games.

Instead of tearing through the JV Bears secondary, he looked flustered by the interior pass rush and produced 87 yards passing. His previous low this season was 184 yards in a loss to the Cowboys.

If the Rams are able to avoid COVID cases and bring a representative team to Minnesota on Sunday, they will test Cousins' composure and Zimmer's ability to rally a team in what is often the most important month of the regular season.