## Patriots or Colts Undefeated?

With the impending showdown between the NFL's top two teams, a lot of the discussion has mentioned the possibility of either the Patriots or Colts going undefeated. Not since the '72 Dolphins went 14-0 in the regular season has an NFL team repeated the feat. There are now 16 games in a regular season, making the achievement even more improbable.

Of course, only one of the two teams could go undefeated this year because they have to play each other. In this post, I'll examine which team is more likely to go 16-0--assuming each wins on Sunday.

The probability that either team would go undefeated is estimated based on a calculation of game-by-game win probabilities. Every permutation of outcomes of wins and losses is computed for each team. The combination that represents only wins and no losses is the probability that the team will be 16-0. The methodology is explained more fully in this post. In short, the probability estimate accounts for all major phases of team efficiency, to-date opponent strength, future opponent strength, and home field advantage in upcoming match-ups.

However, there is one important distinction between teams at this point. Still awaiting their bye, the Patriots and have played, and won, one more game than the Colts. This gives them a distinct advantage when comparing the two teams' chances of winning out. But it is still interesting to know just how possible it is for teams like the Patriots or Colts to do what hasn't been done for three and half decades.

And of course, it all depends on who wins on Sunday.

Both teams have been mercilessly efficient so far in 2007. Below are the efficiency stats for each team (unadjusted for opponent). Also listed is the NFL average (not including NE and IND) for each stat, so we can compare see just how good these two teams are.

 Stat IND NE NFL O Pass 7.57 8.65 6.01 O Run 4.42 4.19 4.05 O Int Rate 0.013 0.011 0.032 O Fum Rate 0.013 0.015 0.027 D Pass 4.79 5.09 6.25 D Run 4.06 4.24 4.05 D Int Rate 0.039 0.042 0.031 Pen Rate 0.21 0.31 0.37

(Pass and run stats are yds per attempt. Fumble rate is fumbles per play. Int rate is in interceptions per attempt. Penalty rate is penalty yards per play.)

NE has the better passing game, but IND has the better running game and defends the pass better. NE gets more interceptions, but IND commits fewer penalties for fewer yards. All things considered, the two teams are about equal. NE has garnered more attention so far because of the fact they've scored more touchdowns, but they've played a considerably weaker schedule.

Below is a table of each team's to-date opponents and their generic win probability (GWP)--the probability a team will beat a notional league-average team at a neutral site. Opponent strengths do account for the beatings handed to them by IND and NE. In other words, NE's strength of schedule isn't penalized due to the pounding their opponents received at the hands of NE themselves. IND's opponents' have been slightly stronger than average with a 0.52 GWP, while NE's opponents' have been below average with a 0.45 GWP.

 NE Opp GWP IND Opp GWP NYJ 0.23 NO 0.32 SD 0.62 TEN 0.58 BUF 0.43 HOU 0.34 CIN 0.50 DEN 0.66 CLE 0.38 TB 0.76 DAL 0.71 bye MIA 0.23 JAX 0.64 WAS 0.50 CAR 0.33 Avg 0.45 0.52

Although both teams are about equal in (unadjusted) efficiency stats, after adjusting for opponent strength IND comes out on top with a 0.92 GWP compared to a 0.90 GWP for NE. Keep in mind these are estimations, so a difference of 0.02 is essentially a wash. We'll certainly find out more on Sunday.

Given about a 90% chance of winning a game against a league-average opponent at a neutral site, and assuming they win against the Colts, the Patriots would roughly have about a 0.907 = 48% chance of going undefeated. If the Colts win Sunday, they would have about a 0.928 = 51% chance of finishing undefeated.

But NFL games aren't against theoretical league-average opponents, and they aren't (normally) at neutral sites. NE has an slightly easier forthcoming schedule as their future opponents' GWP average is 0.43 while IND's future opponents average a slightly tougher 0.45 GWP.

 NE Opp GWP IND Opp GWP bye SD 0.62 BUF 0.43 KC 0.44 PHI 0.55 ATL 0.29 BAL 0.34 JAX 0.64 PIT 0.72 BAL 0.34 NYJ 0.23 OAK 0.31 MIA 0.23 HOU 0.34 NYG 0.53 TEN 0.58 Avg 0.43 0.45

NE's upcoming schedule and their associated outcome probabilities are listed below. The series probability that the a team would go undefeated is the product of the probabilities of winning each individual game. Keep in mind this assumes each team wins this Sunday.

 Vprob Visitor Home Hprob 0.90 NE BUF 0.10 0.08 PHI NE 0.92 0.93 NE BAL 0.07 0.16 PIT NE 0.84 0.02 NYJ NE 0.98 0.02 MIA NE 0.98 0.85 NE NYG 0.15

Probability of New England going undefeated =
0.90 * 0.92 * 0.93 * 0.84 * 0.98 * 0.98 * 0.85 = 0.52

IND's upcoming schedule and their associated outcome probabilities are listed below.

 Hprob Visitor Home Vprob 0.83 IND SD 0.17 0.05 KC IND 0.95 0.95 IND ATL 0.05 0.10 JAX IND 0.90 0.94 IND BAL 0.06 0.95 IND OAK 0.05 0.03 HOU IND 0.97 0.08 TEN IND 0.92

Probability of Indianapolis going undefeated =
0.83 * 0.95 * 0.95 * 0.90 * 0.94 * 0.95 * 0.97 * 0.92 = 0.54

By the end of Sunday's game, one of the teams will see their chances swiftly go to zero.

Note: Republished with a correction to NE's probability.

### 7 Responses to “Patriots or Colts Undefeated?”

1. Tarr says:

No comment except that I really enjoyed reading that. Thanks for putting it together.

2. Tarr says:

Actually I lied, I have two comments:

1) Accuscore, which works by simulating game results, comes up with nearly the exact same probability of the Pats going undefeated (60%) as you do, after a win. They don't mention the odds they give for the Colts, but I would assume that it is lower, as they rate the Pats as a superior team.

2) Neither analysis considers the very significant monkey wrench: at the Giants, week 17, Pats are 15-0, Giants need a win for playoff position, Giants are a pretty good team, Pats have clinched home field, Brady/Moss/et al play one series. Of course, it's hard to account for that situation.

3. Steve Austin says:

Using your VProbs, I come up with 0.56 for the Patriots and 0.54 for the Colts.

Either my arithmetic is suspect, or yours is. ;-\

It also looks like you pulled the wrong VProbs from your table into the Patriots product (e.g. three 0.98 factors instead of two).

4. Brian Burke says:

That's my Excel skills that are suspect. Thanks for a great catch, Bionic Man.

Corrected.

5. Carlos says:

Clicked over from FootballOutsiders.

Great analysis!!

6. 24frames says:

I see that you made some corrections, but now you are missing the Patriots game against Philadelphia in your calculations.

I made the calculations with the Eagles included, and now the Patriots have a 0,528 chance of going undefeated which is actaully less than the Colts, who need to play one more game than the Patriots.

By the way, can't wait for the Patriots - Colts game :)

7. Brian Burke says:

I botched this one. I finally fixed the spreadsheet. But I wouldn't have made the mistake in the first place had I just used a calculator to check my own math.

In any event, it's about a 50/50 proposition for either team, assuming they win Sunday.

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