Jun 16

The Mathletics Behind Playoff Upsets, Part 1

Recent Upheaval in the NFL
For a long time, the rule of thumb in the NFL used to be that earning a first-round bye in the playoffs was a near-necessity to make the Super Bowl. However, from 2005 to 2012, that rule seemed to go by the wayside. Six “long shots” won the Super Bowl in that eight-year span, along with a seventh team that reached the sport’s biggest show. New boundaries could be opening up in the NFL playoffs, creating a wild array of playoff upsets in recent years. Just to make a quick list:

  • 2005: The AFC sixth-seeded Pittsburgh Steelers win Super Bowl XL to become the first team to win three road games in the playoffs and win the Super Bowl. They beat the NFC’s top seed in the victory.
  • 2006: The AFC third-seeded Indianapolis Colts win Super Bowl XLI despite finishing dead last in rushing yards per attempt allowed since the NFL-AFL merger. They also beat the NFC’s top seed in the victory.
  • 2007: The NFC fifth-seeded New York Giants win Super Bowl XLII to become the second 10-6 team to win the Super Bowl. They did so by defeating the 16-0 New England Patriots in what may be the greatest upset in NFL history.
  • 2008: The NFC fourth-seeded Arizona Cardinals lost Super Bowl XLIII after allowing a last-minute touchdown. However, they became just the second 9-7 team to make the Super Bowl.
  • 2010: The NFC sixth-seeded Green Bay Packers win Super Bowl XLV to become the second six seed and third 10-6 team to win the Super Bowl. They also became the third team in NFL history to win the Super Bowl after winning three road playoff games.
  • 2011: The NFC fourth-seeded New York Giants win Super Bowl XLVI to become the first 9-7 team to win the Super Bowl. They did so after beating the 15-1 Green Bay Packers in the divisional round, which may be the biggest upset in that round’s history. More so, the Giants became the first NFL Champion to be outscored in the regular season.
  • 2012: The AFC fourth-seeded Baltimore Ravens win Super Bowl XLVII despite four of their final five regular-season games to finish 10-6 for the year. Ray Lewis retired as a two-time NFL champion.

Excluded on this list is the 2009 season, when each conference’s top seed reached the Super Bowl. That happened again in the 2013 season, when the Seahawks won Super Bowl XLVIII, 43-8, and became one of the best champions of the Super Bowl era. Seattle could break the trend that possibly created new standards for what constitutes a “long shot.” Then again, there may no longer be the “long shot” in the NFL playoffs any more. Overall, the results are rather interesting as to which seeds win the Super Bowl.

Table 5: Super Bowl Champions by Seed (since 1975)

Years 1 2 3 4 5 6
2002-2014 4 3 1 2 1 2
1990-2001 7 3 0 2 0 0
1975-1989 11 2 1 1 0
Total 22 8 2 5 1 2
Percent 55 20 5 12.5 2.5 5

Table 6: Conference Champions by Seed (since 1975)

Years 1 2 3 4 5 6
2002-2014 13 5 2 3 1 2
1990-2001 12 8 0 4 0 0
1975-1989 19 6 2 2 1
Total 44 19 4 9 2 2
Percent 55 23.8 5 11.3 2.5 2.5

PLAYOFF FORMAT NOTES: The NFL realigned in 2002 to have four divisions in each conference, meaning no wild card teams can host a first-round playoff game. Also, the NFL expanded to a 10-team playoff system in 1978, as well as to a 12-team playoff system in 1990.
PLAYOFF SEEDING NOTES: From 1966-1974, home teams were decided by rotation. Seeding system began in the 1975-76 season. Therefore, the first nine Super Bowl Champions are not accounted for in this study. Before the Super Bowl, there were no seeds.

Just to note, each seed won a Super Bowl over the past 10 seasons. The one seeds won three Super Bowls, but they all came against fellow one seeds. They are also 3-7 in Super Bowl games during that span. In fact, the last one seed to beat a lower seed in the Super Bowl was the 2003 New England Patriots winning Super Bowl XXXVIII, and that’s the only such victory since 2000. The one seeds hold a 4-11 Super Bowl record in that time, but 18-11 before that. Thus, one seeds are 22-22 in Super Bowls since seeding in 1975.

Meanwhile, four and six seeds also won multiple Super Bowls over the past 10 seasons. This helps to allude to the wide-spread trend of Super Bowl winners since realignment. This could be a relevant source of correlation, or it could happen to coincide with an outlier eight-year span of unlikely teams to make the league championship round. It all remains to be seen.

For another oddity, to add to the one seeds’ .500 record, three seeds are 2-2 and five seeds are 1-1. Only four seeds (5-4) and six seeds have a winning record (2-0), while only two seeds have a losing record (8-11).

To expand upon the recent changes in playoff upsets, note that home teams suffered as many Divisional Round losses (14) from 2005 to 2012 as they did in that same round (14) from 1987 to 2004. That’s comparing an eight-year span to an 18-year span! In total, home teams were 18-14 in the Divisional Round from 2005 to 2012, only to go 6-2 since then. From 1975 to 2004 (excluding the strike-shortened 1982 season), home teams went 86-30 in the Divisional Round. That’s a 74.14 win percentage dropping down to 56.25 percent, only to return to 75 percent. If you compare the three time periods, you may start to see an argument that we faced an outlier. However, we need to see more from 2015 and beyond to better develop that argument.

Some believe that realignment itself caused the recent turmoil in the NFL postseason, but part two of this study will investigate if the recent outburst of upsets has to do more with simple regression to the mean or a near decade-long fluke.

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