If the N.F.L. season ended today, there would be no playoffs or Super Bowl because too few teams are worthy of the postseason. Or perhaps it just feels that way because so many of the league’s top contenders are reeling from recent upsets.

The Buffalo Bills lost to the hapless Jacksonville Jaguars on Sunday. The Dallas Cowboys lost to the middling Denver Broncos. The lowly Giants took down the surging Las Vegas Raiders.

The Los Angeles Rams lost to the Tennessee Titans, who were without running back Derrick Henry, the bulldozing focal point of their offense. Tom Brady’s Tampa Bay Buccaneers lost to the injury-plagued New Orleans Saints before their bye in Week 8; the Saints celebrated on Sunday by losing to the Atlanta Falcons. And while not technically an upset, the Green Bay Packers lost to the scuffling Kansas City Chiefs, due in large part to Aaron Rodgers’s Covid-related absence.

Upsets are practically baked into the N.F.L.’s “Any Given Sunday” ethos of leaguewide parity. Yet the results of the last two weeks have caused chaos for anyone trying to handicap the playoff field. Heck, since the Giants beat the Saints who beat the Buccaneers, and the Jets beat the Titans who beat the Rams, it can be argued (not at all convincingly) that the Giants should face the Jets in the Super Bowl.

If upsets are truly on the uptick, here are some likely causes:

Penalties

Examine an upset closely and you’ll often find a major penalty-yardage disparity. For example, the Bills committed 12 penalties for 118 yards in their loss to the Jaguars, hampering themselves on both offense and defense. The Buccaneers committed 11 penalties in their Week 8 loss, the Saints just two.

Three categories of penalties in particular may favor the underdog this season:

Roughing the passer: Officials now call roughing the passer 0.56 times per team per game, the highest rate in history. Because this foul often transforms a sack or turnover into a positive result for the offense, it can operate like a winning lottery ticket for the weaker team, assuming the quarterback survived what’s more likely to be a shove than a serious blow.

Defensive Pass Interference: This foul occurs 1.18 times per team per game in 2021, according to NFLpenalties.com, again the highest rate in history. This year’s increase appears to be caused by desperate quarterbacks hurling off-target passes downfield and hoping that defenders crash into their receivers while chasing them. A penalty that favors inaccurate quarterbacks naturally favors underdogs.

Taunting: Any infraction that punishes players for being a little too proud of their accomplishments is likely to work against the better team.

Going for It

Teams attempt fourth-down conversions more than ever: 1.42 times per team per game in 2021, up from just 0.57 times per team per game five years ago. While analytics dictate that “going for it” is usually the correct tactic, a failed conversion can create a dramatic swing in the underdog’s favor.

The Cowboys last week failed two fourth-and-short conversions in the first quarter, one of them within field goal range. Had they punted and kicked a field goal in those situations, Dallas might still have lost, but not so dramatically (they trailed, 30-0, at one point) that it attracted national attention.

Overconfidence and Distractions

“Distractions” is a bit of football speak that can cover a wide range of situations, from a wide receiver wanting more passes thrown his way to a franchise quarterback declaring on YouTube that the contrails behind airplanes cause male-pattern baldness.

Overconfidence can be dangerous for a team of young athletes riding high on recent success. The Cowboys, in particular, have a reputation for declaring themselves the Super Bowl champions in early November.

Distractions and overconfidence can also be post-hoc rationalizations for failures. “Overconfidence” may have caused those Bills penalties or failed Cowboys conversions, but it may also just be a narrative device to explain a few prosaic mistakes.

As for distractions, the Cleveland Browns defeated the Cincinnati Bengals, 41-17, after announcing their plans to waive the eccentric wide receiver Odell Beckham Jr. Now, all of the franchise’s misfortunes have been retconned as Beckham’s fault, dating to Earnest Byner’s fumble in the 1987 A.F.C. championship game.

Course Corrections

The Arizona Cardinals’ 38-13 drubbing of the Titans in Week 1 looked like a stunning upset at the time. It is now clear that the Cardinals were budding Super Bowl contenders.

The Bengals were 5-2 when they fell to the Jets in Week 8. Last week’s blowout loss to the Browns reveals that they were not as strong as their record suggested.

A series of overmatched opponents can leave a team primed for an upset. The Rams, for example, feasted on the Giants, Detroit Lions and Houston Texans before facing the Titans. Again, overconfidence could be blamed, but it’s more likely that the Rams weren’t as good entering Week 9 as their record suggested.

Tinder?

The home-field advantage has all but vanished from the N.F.L. Road teams are 58-49 against the spread in 2021 (54.2 percent), while road underdogs are an even better 36-26 (56.2 percent) against the spread. Similar splits last year were attributed to empty stadiums, but of course that is no longer a factor.

The analytics community is flummoxed by the disappearance of an advantage as old as professional sports itself. Some experts speculated that a similar trend in the N.B.A. was caused by online dating apps like Tinder: Athletes on the road can now enjoy both a romantic escapade and a refreshing night’s sleep, instead of the either-or scenario of the past.

N.F.L. players are typically older than N.B.A. players and endure far less grueling road trips, and it’s a stretch on many levels to attribute upsets to convenient canoodling. The Tinder theory was only posited here in the name of scientific rigor.

Perception

It turns out that only six teams that were favored by 7 or more points in a game this season have lost outright. Fourteen favorites lost under such circumstances through 16 games in both 2020 and 2019. While trends in penalties and fourth-down conversions bear monitoring, upsets might not be on the rise at all; we may simply be reacting to a spate of dramatic ones in Week 9.

At a rate of nearly one major upset per week, the N.F.L.’s Any Given Sunday mission statement still holds true. Some Sundays just give more than others.