The Green Bay Packers will enter the 2021 NFL playoffs on a roll. We don't know what will happen this week -- the Packers might sit starters and lose to the Detroit Lions -- but Green Bay has won five straight going into the final week of the season. On Sunday night they had their most substantial victory of the season with a 37-10 win over Minnesota.
It doesn't quite stand out as it did in past years because December is no longer the end of the regular season, but it is worth noting that seven teams were unbeaten in the month of December this year: Dallas, Green Bay, Indianapolis, Kansas City, the Los Angeles Rams, Miami and Philadelphia. It also helped that bye weeks meant some of those teams had only three December games. But still, in the past 40 years, the only other time there were at least six unbeaten teams in December was 1986.
So how much does it matter for a team to finish the season on a roll? Is it important for NFL teams to be peaking at the end of the regular season? Or is peaking in the postseason the only thing that really matters?
Let's take a look with the help of Football Outsiders.
How we measure
One way to look at teams getting hot at the end of the season is with weighted DVOA. Football Outsiders uses our DVOA metric to measure teams over the entire season, but we also have a metric called weighted DVOA that gives less weight to early-season games to get a better idea of how well teams are playing right now.
Weighted DVOA is not strictly the same as looking at only December games or at just the last four or five weeks of the season. But the gap between weighted DVOA and full-season DVOA is a useful measurement of which teams played better or worse in November and December. The advantages of DVOA include that it knows the value of a blowout win and that it adjusts for schedule so that teams aren't considered "hot" when they post a three-point win over an opponent that's just playing for draft position.
What the numbers show
Fifteen of the 38 teams that led the NFL in weighted DVOA at the end of the regular season went on to make the Super Bowl, and 11 of those teams won the title. By comparison, 18 teams that led the NFL in full-season DVOA went on to make the Super Bowl, with 14 of those teams winning the title. Those numbers are pretty close.
The only two champions who led the league in weighted DVOA but not in full-season DVOA were the 1994 San Francisco 49ers (third for the full season) and the 2003 New England Patriots (fourth). Each of those teams spent the season recovering from a particularly famous early-season loss: San Francisco losing 40-8 to Philadelphia in Week 5 of 1994 when George Seifert benched Steve Young, and New England falling 31-0 to Buffalo on opening day of 2003, the game that famously inspired Tom Jackson to declare that the Patriots players "hate their coach."
Suppose that instead of looking at whether teams that finish the season hot made the Super Bowl, we look at whether teams that made the Super Bowl finished the season hot. Out of 76 teams to make the Super Bowl, 42 of them (55%) had a higher weighted DVOA than full-season DVOA. If you want to look just at the end of the season, 43 of those teams (57%) had a higher DVOA in their final five games than their full-season DVOA. That at least suggests there's some advantage to finishing the season better than you started it. But that advantage is pretty small.
Or we could open things up to look at all playoff teams. Let's take the playoff team from each year with the biggest positive gap between weighted DVOA and full-season DVOA: the team each year that was hottest at the end of the season compared with early in the season. This year that would be New England; last year it was Buffalo; and so on. Over the past 38 years, these teams had a combined record in the postseason of 34-35. So, no clear advantage there.
Now let's take the playoff team from each year with the biggest negative gap between weighted DVOA and full-season DVOA. These are the teams that were hot early on but snuck into the playoffs despite playing poorly late in the year. This year, that's likely Arizona; last year it was Pittsburgh; and so on. Over the past 38 years, these teams had a combined record in the postseason of 35-35. That's a tiny bit better than the postseason record of the hot teams!
What history says: Cold teams entering the playoffs
Anecdotally, recent NFL history is filled with teams that struggled in December only to turn things around and go on a run to the Super Bowl.
2012 Baltimore Ravens
They lost four of their final five games, plummeting from 9-2 to 10-6. Although they had the excuse of playing mostly backups in a meaningless Week 17 game, they still entered the postseason anything but hot. In the playoffs, they were red-hot, with four straight victories to win the Super Bowl despite finishing the season just 10th in DVOA.
2009 New Orleans Saints
They won their first 13 straight, but the last two of those victories were close three-point wins over mediocre Washington and Atlanta teams. Then the Saints lost their last three games, including a Week 16 contest against the 2-12 Buccaneers. The final loss came with mostly backups in a meaningless game against Carolina, but still "we followed up two losses by losing again with backups" is not exactly the definition of entering the playoffs hot. It didn't matter when the Saints blew away the Cardinals, slipped past the Vikings in overtime and then vanquished the Colts to win their first Super Bowl title.
2008 Arizona Cardinals
They lost four of their final six games, including losses of 48-20 to Philadelphia, 35-14 to Minnesota and 47-7 to New England. That's the Matt Cassel Patriots, not the Tom Brady Patriots. In the playoffs, the Cardinals won three straight and came within 42 seconds of taking home the Vince Lombardi Trophy against Pittsburgh in Super Bowl XLIII.
What history says: Hot teams entering the playoffs
On the other hand, some of the hottest teams from the end of the season didn't even win a game in the playoffs:
2010 New England Patriots
This team finished the year with eight straight wins. Its final five games included one close win over Green Bay and then scores such as 38-7 over Miami, 34-3 over Buffalo, 36-7 over Chicago and 45-3 over the New York Jets. The Patriots had the highest weighted DVOA ever for a team at the end of the regular season. Then, that same Jets team upset the Patriots 28-21 in the divisional round.
2009 San Diego Chargers
San Diego started the season 2-3 and then won 11 straight games. The Chargers' last two months included blowouts such as 32-3 over Denver, 43-14 over Kansas City and 42-17 over Tennessee. The same Jets team that would upset the Patriots the next year also took out the 2009 Chargers in the divisional round, winning 17-14.
1993 Houston Oilers
This Oilers team started 1-4 and then won 11 straight games. Houston gave up just 11.3 points per game over that win streak and finished it off with a 24-0 stomping of a Jets team that was still in playoff contention. Then Kansas City beat the Oilers 28-20 in the divisional round, ending their pursuit of a title.
There's also plenty of anecdotal evidence where teams that ended the season hot did go on to win the Super Bowl. In recent years, the 2014, 2016 and 2018 Patriots all finished the season with a higher weighted DVOA than full-season DVOA. So did last year's Tampa Bay Buccaneers. Seven of the past eight Super Bowl champions had a higher DVOA rating in their final five games than they had for the season as a whole.
So, does peaking before the playoffs matter?
When you put all that data together, you don't really get a clear picture either way. It's probably better to finish the season strong than it is to start off strong and stumble at the end. But the difference is small. A hot end to the season isn't necessarily a sign of a team that's ready to march to the championship, and a bad December doesn't mean you have to write off your favorite team as it enters the playoffs.