One notable difference between the regular season and the playoffs is that the higher seeded playoff team hosts the game. If the seedings reflect the actual strength of the teams, we should expect to see a larger winning percentage for home teams than in the regular season. Teams that win on the road through the playoffs would be truly remarkable teams.
In this post I'll look at road winners in each round of the playoffs from 1994, the year the salary cap began, through 2006, the most recent year. I'll also look at differences in road winners from two different playoff periods. The first period is from 1994-2001, when the playoffs featured 3 division winners and 1 wildcard team from each conference. The second period is from 2002-2006 when the playoffs featured a 4th division winner and two wildcard teams. The sample sizes aren't terribly large, but large enough to begin to see some possible trends.
The first table lists each round of the playoffs for the entire post-salary cap period, and the number and percentage of road winners. Overall road teams won 33% of games in the playoffs. This is in contrast to the normal 42-43% rate in the regular season.
1994-2006 | Games | Road Wins | Road Win% |
Conference | 26 | 11 | 42 |
Division | 52 | 13 | 25 |
Wildcard | 52 | 15 | 29 |
All Rounds | 130 | 39 | 32 |
The next two tables break up the data into the two playoff periods. The first table lists the road winners from '94-'01. The second table lists them from '02-'06, featuring the NFL's current playoff structure.
1994-2001 | Games | Road Wins | Road Win% |
Conference | 16 | 6 | 38 |
Division | 32 | 7 | 22 |
Wildcard | 32 | 7 | 22 |
All Rounds | 75 | 20 | 29 |
2002-2006 | Games | Road Wins | Road Win% |
Conference | 10 | 5 | 50 |
Division | 20 | 6 | 30 |
Wildcard | 20 | 8 | 40 |
All Rounds | 50 | 19 | 40 |
Again, the sample sizes aren't large, but we can make some observations. First, the playoff seedings do appear to reflect a stronger home team winning percentage. The better team is probably seeded higher and hosts the game. But this effect could also be due to the "dome at cold" effect. With bitter cold weather in most cities in January, dome teams would be at a severe disadvantage when playing on the road outdoors. In fact, of the 14 "dome at cold" match-ups, dome teams have won only 2 (14%), which is same the rate as in December in the regular season.
The conference championship games reflect a relatively high number of road winners (40%). This makes sense for a couple reasons. Low-seeded dome teams have already been eliminated. Also, the games feature the closest match-up between relative team strength. They ostensibly would feature the two best teams at the time (the true 1 and 2 seeds), regardless of their official seeding.
Third, there is a noticeable difference between the '94-'01 wildcard rounds and those of '02-'06. Road teams have been winning more frequently lately in the wildcard round (40%, vs 29%). There isn't enough data yet to make any firm conclusions, but it makes sense intuitively.
I think we're seeing more road winners or "seed"-upsets due to the new division structure. With four division winners in each conference, it's more likely an average team can luck into the division championship, especially with a weak division. With only four teams in each (compared to five or six previously), it's more likely to have a thoroughly weak division. The wildcard teams, which are road teams by rule, are probably from the stronger divisions and possibly stronger teams than their seeding indicates. Similar to the conference championship games, the modern wildcard round feature games between closely seeded teams (5 vs. 4) and (3 vs. 6).
This year, the two 5 vs. 4 seed games are expected to be toss-ups. JAX is slightly favored over division-winner PIT by 2.5 points, and TB is favored over NYG by 2.5 points. SEA, the division winner of the clearly weakest division, is only favored over WAS by 3.5 points.
Last time I looked at this, I regressed playoff home win% on regular season home team strength and away team strength. The intercept was something like .6, which is, IIRC, close to the home field advantage in the regular season. I'll see if I can dig up that data.
Sorry, I should have credited pro-football-reference.com for the data. Thanks.