But it happens. Sometimes a mediocre team sneaks in. Other times, a team that built a strong record early in the season is fading hard by playoff time. Injuries factor in.
This season we have two double-digit underdogs at BetMGM on wild-card weekend. The Seattle Seahawks are 10-point underdogs at the San Francisco 49ers. The Miami Dolphins, with their quarterback injury questions, are 10.5-point underdogs at the Buffalo Bills.
Double-digit underdogs have done fairly well through the past couple decades, though a lot of that positive history happened a while ago. Big dogs haven't been such a good bet lately.
How have big favorites done in the NFL playoffs?
Since 2000, there have been 25 double-digit spreads in NFL playoff games according to Stathead. The largest spread was New England Patriots at -16 over the Houston Texans in the 2016 playoffs. The Patriots won 34-16, covering the spread.
But the rest of those teams that oddsmakers give little chance to win have actually done fairly well. Teams that are double-digit underdogs since 2000 have pulled seven straight-up upsets. That's not too bad. Consider how big of a shock it would be if the Seahawks or Dolphins won this weekend.
2001 AFC championship: New England (+10) beat Pittsburgh 24-17
2001 Super Bowl XXXVI: New England (+14) beats St. Louis 20-17
2007 AFC divisional: San Diego (+11) beats Indianapolis 28-24
2007 Super Bowl XLII: N.Y. Giants (+12.5) beat New England 17-14
2008 NFC divisional: Arizona (+10) beats Carolina 33-13
2010 NFC wild card: Seattle (+10) beats New Orleans 41-36
2019 AFC divisional: Tennessee (+10) beats Baltimore 28-12
The one thing that stands out about that list is the double-digit upsets haven't happened much often. Since that 2010 Seahawks win in the famous "Beast Quake" game, double-digit underdogs are just 1-12 straight up. Still, most bettors just want to know if the Dolphins and Seahawks can cover.
Rough road for big playoff underdogs
Again using the "Beast Quake" game as a cutoff point, that's when big underdogs started struggling to even cover the spread.
Starting in the 2010 divisional round, there have been 13 double-digit underdogs. Those teams are 2-11 against the spread. Only the Titans at the end of the 2019 season pulled off a win. In the 12 other games the average margin of victory is 17.4 points for the favorites. The only time a double-digit underdog has covered and not won since the 2011 wild-card round was Washington, losing 31-23 as a 10-point underdog against the Tampa Bay Buccaneers in the wild-card round at the end of the 2020 season. Taylor Heinicke was pressed into starting for Washington due to injuries and helped keep his team in the game.
If there's a reason for the shift with double-digit underdogs' success, it could be that oddsmakers are a little more careful with the biggest point spreads. They only save it for lopsided matchups that truly deserve those huge spreads, and therefore we won't see a lot of lively double-digit underdogs.
Or perhaps it's just a small sample of 13 games and we'll see a shift starting this week. Just know that if you're taking the Dolphins or Seahawks this week, recent history isn't on your side.