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Playoff Tiebreakers

Posted by Jason Lisk on December 30, 2008

Back when their were only two divisions in the NFL and only the winners of each division met in the championship game, playoff tiebreaker rules were not all that necessary. On the occasions when two teams would tie for a division lead, they would simply push back the date of the league championship game by a week, and have a one-game playoff between the tied teams, and let them settle it on the field. But now, with so many more teams and divisions, vastly different schedules, many more playoff teams, and set schedules for games to occur thanks to television, we can't simply delay the playoffs and have play-in games to break ties.

The first, and only, case of a tiebreaker deciding a playoff spot prior to the AFL-NFL merger was a notable one. In 1967, the Baltimore Colts entered the final week of the regular season at 11-0-2, trying to become the first team to go undefeated since the 1929 Green Bay Packers. However, they had to travel to Los Angeles to face the 10-1-2 Rams, their Coastal Division rival. The Rams won that game, and the tiebreaker, on net points scored in the two head to head matchups, and advanced to the playoffs. The Colts, despite tying for best record in the league, stayed home.

After the merger, the occasional division tiebreaker came into play, but conference tiebreakers were rare because, until 1975, the playoff seeds were determined by a set rotation for home games, and were not based on record. The tiebreakers became far more common once the league went to a seeding system for the conference playoffs, then added a wildcard game in 1978. Using the official tiebreaker explanations contained in The NFL Record and Fact Book, I have recorded every tiebreaker that has been used to determine either a) a division winner, b) finish within a division for potential wildcard spot, c) seeding within a conference among division winners, or d) seeding within a conference among potential wildcard eligible teams. Every potential tiebreaker was recorded with a couple of things in mind. First, all ties within a division are broken before ties are broken across divisions. Second, if a 3-way tie (or more) can be broken affirmatively, that is, by one team winning the tiebreaker outright in a category, then the remaining teams revert to a new tiebreaker, even if the second team was ranked ahead of the third team in that category. Only if the top two teams tie in a tiebreaker and the third does not is it broken negatively, that is, by kicking out the third team and re-running the tiebreaker again with only the top two teams. Third, if, after a 3-way tiebreaker was decided, there were no more available playoff spots, then I did not further break the tie between the remaining teams. Thus, I am only looking at ties that had a material impact on the playoffs, and not those that merely determined division finish for scheduling purposes the following season.

Inspired by this post, where Doug looked at the question of whether head to head was the right tiebreaker for college football by building a model, I wanted to check the various tiebreakers used in the NFL to see which ones actually appear to be better. To do that, I'm going to use both Simple Rating System regular season ratings of the teams (to see how often the "better" team by SRS wins a certain tiebreaker), as well as actual playoff results.

Prior to this season, 116 two team tiebreakers, 19 three team tiebreakers, and two four team tiebreakers have been used to determine a playoff position since 1970. One of the four team tiebreakers was back in the strike-shortened 1982 season; the other was in 2006 when the Giants got the final wildcard at 8-8 over Green Bay, Carolina and Saint Louis. Here are the current NFL tiebreaking procedures. We can now add a tiebreaker for the AFC East between Miami and New England (decided by conference record), for the AFC West between San Diego and Denver (division record), a tiebreaker between the New York Giants and Carolina for the #1 seed (head to head), and between New England and Baltimore for the final wildcard spot in the AFC (conference record).

I'm going to use the following codes to summarize the various tiebreakers that have been used over the years.

H2H= Head to Head Victory
DIV = Better record in divisional games
CNF= Better record in conference games
OPP= Better record in games against common opponents
NPD= Better Net Point Differential in Divisional Games
HPD= Better Net Point Differential in Head to Head Games
NPC= Better Net Point Differential in Conference Games
NPA= Better Net Point Differential in All Games
SOV= Strength of Victory
COL= Fewer Losses by Common Opponents
PRS= Point Rating System

To be honest, I don't even know how the last two tiebreakers were determined, and they don't exist anymore. "COL" was used to determine the NFC Central in 1977 between Minnesota and Chicago, but I can't figure out how the common opponents could have fewer losses for Minnesota, since they are, well, common opponents. And I have no idea what the Point Rating System was, but it was used in 1975 to place Minnesota as the #1 seed ahead of the Los Angeles Rams, in the first year the league seeded the conference teams.

In Divisional tiebreakers, five three way ties have been used. Four were determined affirmatively by head to head record (that is, one team had either a 3-1 or 4-0 record combined against the other two), and one, the AFC East in 2002, was determined in the negative by kicking out Miami based on division record (2-4 versus 4-2 for both the Jets and Patriots). Here is a breakdown of how often each of the remaining tiebreakers were used to break a two way tie between division opponents.

Two Team Division Tiebreakers
===================================
	H2H	18	
	DIV 	14		
	CNF	12		
	NPD	4		
	OPP	2		
	HPD	1		
	COL	1		
===================================

Virtually all the divisional tiebreakers have been decided by either head to head, division record, or conference record, with head to head being the most common.

For conference tiebreakers, we have had the two aforementioned four-team ties, and fourteen three-team tiebreakers, all of which were broken by the conference record tiebreaker (12 affirmatively, and 2 by kicking out the bottom team and reverting to a two team tiebreaker). Here is a breakdown of how often each of the remaining tiebreakers were used to break a two way tie between division opponents.

Two Team Conference Tiebreakers
===================================
	CNF	27
	H2H	24		
	OPP	12
	SOV	2
	NPC	1
	NET	1
	PRS	1
===================================

Here, we see that the "better conference record" tiebreaker has actually been used more commonly than head to head, and those two tiebreaker steps have resolved 75% of the conference ties. Only record against common opponents has also figured on more than a rare occasion.

Now, let's see which tiebreakers do the best job (as that is defined by both SRS ratings and actual head to head results in the playoffs) of selecting the better team to win the tiebreaker. I'm only going to focus on those that have come up on more than a couple of occasions, and am not including any results from this season, as the playoffs are still to come. I'm limiting it to Head to Head, Conference Record, Division Record, and Record against Common Opponents. Before I get to the results, see if you can guess which ones are better or worse.

Okay, time's up.

This table shows the average SRS rating of the tiebreaker winner, tiebreaker loser, the total number of cases, and then shows how many times, according to SRS, the tiebreaker winner was clearly better (SRS at least 1.51 points higher), roughly equal (SRS rating of both teams within 1.5 points), and clearly worse (SRS at least 1.51 points lower), than the tiebreaker loser.

type	Win	Lose	No.		B	C	W
=======================================================================	
H2H	4.73	3.99	40		16	13	11
DIV	2.83	2.88	14		4	4	6
CNF	3.36	3.58	37		14	7	16
OPP	2.94	3.13	14		5	5	4
=======================================================================

It came as a surprise to me, at least until I read Doug's earlier post and thought about the rationale, but the actual results from the last forty years show that head to head is about as good a tiebreaker as there is. For all these tiebreakers, it's no surprise that the teams are roughly equal. But the head to head tiebreaker winners are the only ones that are, on average, better than the losers. The remainder appear to be no better than flipping a coin. But that is some theoretical stuff, and whether you accept it or not depends on how you view the SRS as a proxy of who is actually better.

Many times, the tiebreaker loser doesn't make the playoffs, or never gets a chance to settle the actual question on the field. Occasionally, though, a team that loses out on a tiebreaker gets to later go on the road against the other team. We are dealing with small samples, but here are the results (from the point of view of the home team/tiebreaker winner) when two teams meet in the playoffs that had previously been the subject of a playoff seeding tiebreaker:

TYPE		W	L		PCT
==========================================
H2H		7	3		0.70
NPD		2	1		0.67
CNF		10	7		0.59
DIV		2	3		0.40
OPP		0	2		0.00
==========================================

I've added in Net Point Differential in Division Games because three of the four times it was used, the two division opponents went on to meet in the playoffs. Again, Head to Head tiebreaker winners fare better than anyone when playing the tiebreaker opponent in the playoffs. The Common Opponent tiebreaker winner is 0-2 (Pittsburgh losing at home to San Diego in 1982, and Philadelphia losing at home to the Rams in 1989). The Conference Record Tiebreaker teams fare well in the wildcard round, but on the five occasions two teams have faced each other in the Divisional or Championship round and the home team was determined by conference record, the home team has gone 1-4.

So, Doug asked the question "Is head to head the right tiebreaker?" a couple of weeks ago, and at least for the NFL, the answer appears to be "yes". After that, though, the remaining tiebreakers are suspect. The conference tiebreaker sounds right, particularly since we are seeding for conference playoffs. But the thing is, those teams likely did not play the same conference games. With the current imbalanced conference schedules, the only time this tiebreaker would come into play in a two team tiebreaker is when teams are on opposite sides of the conference slate. This one appears to, somewhat more than half the time, reward the team that played the easier schedule.

The Common Opponent tiebreaker needs to go. The only time it comes into play is, again, when teams are on opposite sides of a conference schedule, have tied on overall conference record, and they will thus have five common games. Consider this, team A plays in a division with Powerhouse, team B plays in a division with Cupcake, and team A played Cupcake in the conference schedule, and team B played Powerhouse. If they perform equally in the other two common games, then Team A is at a disadvantage. Both could lose to Powerhouse (Team A twice and Team B once) and beat Cupcake (Team A once and Team B twice), and Team B wins the common opponents tiebreaker.

What should replace it? I know the league is not going to get into a computer formula situation, but why not use some of the important elements of actually determining the quality of a team--namely strength of schedule or overall point differential. I would think that going with either of these would be better than using something like common opponents (which is unfair to the team that plays the better division opponent) or conference games. The league should also consider moving the strength of victory tiebreaker further up the tiebreaker priority list, ahead of some of the others.

This entry was posted on Tuesday, December 30th, 2008 at 2:47 pm and is filed under General, History, Rule Change Proposals. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.